FORMULATION AND EVALUATION OF FLOATING …

“FORMULATION AND EVALUATION OF FLOATING

MICROSPHERES OF SILYMARIN FOR ENHANCED

BIOAVAILABILITY”

By

Mr. SIVANAGARAJU THATI, B.Pharm.,

Reg. No.10PU421

Dissertation Submitted to the

Rajiv Gandhi University of Health Sciences, Karnataka, Bangalore

In partial fulfillment of the requirements for the degree of

MASTER OF PHARMACY

IN

PHARMACEUTICS

Under the guidance of

Mr. Ganesh N.S., M.Pharm.,(Ph.D).,

Department of Pharmaceutics

Sarada Vilas College of Pharmacy

Mysore

2012

RAJIV GANDHI UNIVERSITY OF HEALTH SCIENCES,

KARNATAKA, BANGALORE

DECLARATION BY THE CANDIDATE

I hereby declare that the matter embodied in the dissertation entitled

“FORMULATION AND EVALUATION OF FLOATING MICROSPHERES OF

SILYMARIN FOR ENHANCED BIOAVILABILITY” is a bonafide and

genuine research work carried out by me under the guidance of

Mr. GANESH N. S., M. Pharm., (Ph.D)., Department of Pharmaceutics,

Sarada Vilas College of Pharmacy, Mysore . The work embodied in this

thesis is original and has not been submitted the basis for the award of

degree, diploma, associate ship (or) fellowship of any other university

(or) institution.

Date:

Place: Mysore Mr. Sivanagaraju Thati, B. Pharm.,

SARADA VILAS COLLEGE OF PHARMACY

KRISHNAMURTHYPURAM - 570004

CERTIFICATE BY THE GUIDE

This is to certify that the dissertation entitled “FORMULATION

AND EVALUATION OF FLOATING MICROSPHERES OF SILYMARIN

FORENHANCED BIOAVAILABILITY” is a bonafide research work carried

out by Mr. Sivanagaraju thati submitted in partial fulfillment for the

award of the degree of “Master of Pharmacy” in pharmaceutics by the

Rajiv Gandhi University of Health Sciences, Karnataka, Bangalore.

Date: Mr. Ganesh N. S., M.Pharm.,(Ph.D).,

Department of Pharmaceutics, Place: Mysore Sarada Vilas College of Pharmacy,

Mysore – 570004.

SARADAVILAS COLLEGE OF PHARMACY

KRISHNAMURTHYPURAM-570004

ENDORSEMENT BY THE HEAD OF THE

DEPARTMENT

This is to certify that the dissertation entitled “FORMULATION

AND EVALUATION OF FLOATING MICROSPHERES OF SILYMARIN FOR

ENHANCED BIOAVAILABILITY ” is a bonafide research work carried out

by Mr. Sivanagaraju Thati submitted in partial fulfillment for the award

of the degree of “Master of Pharmacy” in Pharmaceutics by the Rajiv

Gandhi University of Health Sciences, Karnataka, Bangalore. This work

was carried out by him in the library and laboratories of College of

Sarada vilas Pharmacy, under the guidance of Mr. Ganesh N. S.,

M.Pharm, Department of Pharmaceutics, Sarada Vilas College of

Pharmacy, Krishnamurthypuram ,Mysore.

Date: Dr. C. Jayanthi, M. Pharm. Ph.D., Professor and HOD,

Place : Mysore Department of Pharmaceutics,

Sarada Vilas College of Pharmacy,

Mysore – 570004.

SARADA VILAS COLLEGE OF PHARMACY

KRISHNAMURTHYPURAM -570004

ENDORSEMENT BY THE PRINCIPAL / HEAD OF THE

INSTITUTION

This is to certify that the dissertation entitled “FORMULATION AND

EVALUATION OF FLOATING MICROSPHERES OF SILYMARIN FOR

ENHANCED BIOAVAILABILITY” is a bonafide research work carried out

by Mr. Sivanagaraju Thati submitted in partial fulfillment for the

award of the degree of “Master of Pharmacy” in Pharmaceutics by the

Rajiv Gandhi University of Health Sciences, Karnataka, Bangalore. This

work was carried out by him in the library and laboratories of Sarada

vilas College of Pharmacy, under the guidance of Mr. GaneshN. S,

M.Pharm., Department of Pharmaceutics, Sarada Vilas College of

Pharmacy, Mysore.

Date: Dr. Joshi Hanumanthacher M Pharm., Ph.D., Principal,

Place: Mysore Sarada Vilas College of Pharmacy,

Mysore – 570004.

COPYRIGHT

DECLARATION BY THE CANDIDATE

I hereby declare that the Rajiv Gandhi University of Health

Sciences, Karnataka shall have the rights to preserve, use and

disseminate this dissertation / thesis in print or electronic format for

academic / research purpose.

Date:

Place: Mysore Mr. Sivanagaraju Thati., B.Pharm.,

© Rajiv Gandhi University of Health Sciences, Karnataka.

LIST OF ABBREVIATIONS

Department of pharmaceutics, Sarada Vilas college of pharmacy

BT : Buoyancy Time

CNS : Central Nervous System

°C : Degree centigrade

CDR : Cumulative Percentage Drug Release

Conc : Concentration

DCP : Dibasic Calcium Phosphate

DCM : Dichloromethane

DDS : Drug Delivery Systems

DSC : Differential Scanning Calorimetry

ENT : Ear Nose Tongue

EC : Ethyl cellulose

FDDS : Floating Drug Delivery Systems

FTIR : Fourier Transform Infra red

GET : Gastric Emptying Time

GIT : Gastro Intestinal Tract.

gm : Gram

GRDDS : Gastric Retentive Drug Delivery Systems

GRDF : Gasatroretentive Dosage Form

GRT : Gastric Residence Time

HBS : Hydrodynamically Balanced System

HPMC : Hydroxy Propyl Methyl Cellulose

IP : Indian Pharmacopoeia




KSI : Kilopond Per Square inch

nm : Nanometer

min : Minutes

mg : Milligram

ml : Milliliter

MMC : migrating myoelectric cycle

µg : microgram

PVP : Polyvinyl Pyrolidine

SLM : Silymarin

SLM 1 : SLM to polymers ratio 0.3 :0.7 :1.0

SLM 2 : SLM to polymers ratio 0.3 : 0.7: 1.5





UV : Ultra violet

Vd : Volume distribution

ACKNOWLEDGEMENT

“Gratitude makes sense of our past, brings peace for today and creates a

vision for tomorrow”

The completion of this dissertation is not only fulfillment of my dreams but

also in fulfillment of dreams of my parents and brother and sister who have taken

lots of pain for me in completion of my higher studies.

Through continued blessings of Almighty God, I have completed this

dissertation. Special appreciation goes to my guide Mr. Ganesh N. S., Associate

professor, Department of Pharmaceutics, Sarada Vilas College of Pharmacy for the

belief in my abilities invaluable guidance & ever-lasting encouragement throughout

my course.

I express my deep gratitude to Dr. C. Jayanthi, Head of the Department,

Department of Pharmaceutics, and Sarada Vilas College of Pharmacy for the

valuable guidance during the course of study.

I take a step forward to express my deep regards to Dr. Joshi

Hanumanthachar Principal, Sarada Vilas College of Pharmacy for his enduring

support.

I express my deep gratitude to Mr.GaneshN.S., Dr.C.Jayanthi, Mrs.Roopa

and the entire staff of Sarada Vilas College of Pharmacy for the valuable guidance

during the course of study.

I thank to Mrs.Lakshimi, Mr.Ramesh, Mrs.Chinnama and all non

teaching staff of Sarada Vilas college of Pharmacy for their support.

My Beloved father Mr. Srinivasarao and mother Mrs. Mangama Brother

Mr. Pramod, sisters, Miss. vinupama and my Brother Mr. Prasad For all the

everlasting love and support throughout my life.

“Friend in need are friends indeed”, I thanks to my friends Ravi kiran,

Jamal Sharif , Vijay, Sada Reddy, Siva reddy, Rathnakar , Harsha.

I thank all my classmates Anahitharajoul, Bharathi.G, Devendrapratap

Singh, Ganesh A, Praveen Kumar, Venkatesh , Sada Reddy. I convey my

thanks to my Seniors Vinupama, Anil SN, Paneer Selvem I extend my thanks

to all my juniors.

I thank to my family members my dearest Uncle Mr. Sambhaya, and

Mr. S. purushotham , Mr. Venkatrao and my dearest brother Mr. Pramod,

Prasad.

Of every single second of their life, they spares half of that second for me

and of their every Heart beat, half the beat is for my care……. “PARENTS”.

Last but not the least special thanks to management of the Sarada Vilas

College of pharmacy for providing such facilities for making success of my

project .

Sincerely thanks to all

Date:

Place: Mysore. Mr. SIVANAGARAJU THATI

Affectionately

Dedicated to my

Beloved

Parents

ABSTRACT

Department of Pharmaceutics, Bharathi College of Pharmacy

OBJECTIVE:

To develop and evaluate SLM floating microspheres using polymers like

HPMC E 50 LV nd EC. It is recently developed anti diabetic drug used effectively in

therapeutic practice today. However, the SLM has short half life (4-6) and hence

requires frequent administration. And it has degradation in the intestinal pH Therefore

the possible way by which this can be overcome is by formulating gastro retentive

system a controlled release formulation (CRF).

METHODS:

Floating Microspheres of SLM were prepared by solvent evaporation techniques

by using polymers like HPMC E50LV and EC. Various evaluation parameters were

assessed, with a view to obtain oral controlled release of SLM. In the present study

six formulations were formulated by using HPMC E 50 LV and EC in various

proportions. The prepared SLM floating microspheres were then subjected to FTIR,

SEM, particle size and size distribution, % yield, drug content, entrapment efficiency,

in vitro dissolution studies, release kinetics, and DSC.

RESULTS:

The FTIR Spectras revealed that, there was no interaction between polymers

and SLM. SLM floating microspheres was spherical in nature, which was confirmed

by SEM. SLM floating microspheres with normal frequency distribution were

obtained. A maximum of 89.60% drug entrapment efficiency was obtained. The in

vitro performance of SLM floating microspheres showed controlled release depends

on the polymer concentration. The co-efficient of determination indicated that the

ABSTRACT

ABSTRACT

Department of Pharmaceutics, Bharathi College of Pharmacy

release data was best fitted with zero order kinetics. Higuchi equation explains the

diffusion controlled release mechanism. The diffusion exponent ‘n’ values of

Korsemeyer-Peppas model were found to be Non-Fickian. The DSC pattern shows

that there was decrease in the crystallanity of the SLM.

CONCLUSION:

The present study conclusively demonstrates the feasibility of effectively

encapsulating SLM into HPMC E50LV and EC to form potential controlled release

drug delivery system.

KEYWORDS: Silymarin ; controlled release formulation; floating microspheres.

CONTENTS


CHAPTER NO TITLE PAGE NO

1 Introduction 1

1.1 Novel drug delivery system 1

1.2 Approaches to gastric retention 6

1.3 Floating drug delivery systems 9

1.4 Floating microspheres 15

1.5 Liver 21

2 Objectives of study 24

2.1 Plan Of research work 25

3 Review of literature 26

3.1 Drug Profile 35

3.2 Polymer profiles 40

3.2.1 Hydroxy propyl methyl cellulose E 50 LV 40

3.2.2 Ethyl cellulose 44

4 Materials and Methods 47

4.1 Materials 47

4.2 Methods 49

4.2.1 Preformulation studies 49

4.3 Formulation design of floating microspheres of

Silymarin 50

4.4 Evaluation of floating microspheres of

Silymarin 50

5 Results 56

6 Discussion 77

CONTENTS

CONTENTS


7 Conclusion 82

8 Summary 84

9 Bibliography

10 Annexures

LIST OF TABLES


TABLE

NO TITLE

PAGE

NO

1.1 Marketed Products of floating drug delivery system 20

3.1 Typical viscosity values for 2% (w/v) aqueous solutions of

Methocel, Viscosities measured at 20°C 43

4.1 List of chemicals used with grade and supplier 47

4.2 List of instruments used 48

4.3 Formulation design of SLM floating microspheres 50

5.1 Wave length of maximum absorption of SLM in methanol 56

5.2 Average diameter of SLM floating microspheres 61

5.3 Frequency distribution data of SLM floating microspheres 62

5.4 Buyounancy percentage of SLM floating microspheres 63

5.5 Standard calibration data of SLM in methanol 63

5.6 Drug entrapment efficiency of SLM floating microspheres 64

5.7 In vitro release data of SLM floating microspheres 66

5.8 Zero order release kinetics data of SLM floating

microspheres 68

5.9 First order release kinetics data of SLM floating

microspheres 69

5.10 Higuchi matrix release kinetics data of SLM floating

microspheres 70

5.11 Peppas release kinetics data of SLM floating microspheres 71

LIST OF TABLES

LIST OF TABLES


5.12 Regression co-efficient (r

2) values of different kinetic models

and diffusion exponent (n) of Peppas model for SLM

floating microspheres

74

LIST OF FIGURES

Department of pharmaceutics, Bharathi college of pharmacy

FIG

NO TITLE

PAGE

NO

1.1 Anatomy of the stomach 2

1.2 Classification of gatroretentive drug delivery 9

1.3 Hydrodynamically balanced system 10

1.4 Intra gastric bilayer floating tablet 11

1.5 A multi-unit type oral floating dosage system 11

1.6 Stages of floating mechanism 12

1.7 Intra gastric floating gastrointestinal drug delivery device 12

1.8 Inflatable gastrointestinal delivery system 13

1.9 Intra gastric osmotically controlled drug delivery system 14

1.10 Intragastric floating microbaloons drug delivery system 16

5.1 UV spectra of SLM 56

5.2 IR spectra of SLM 57

5.3 IR spectra of physical mixture of SLM ,HPMC E 50 LV and

EC 58

5.4 IR spectra of floating microspheres using mixture of HPMC E

50 LV and EC 58

5.5 IR spectra of HPMC E 50 LV and EC blank microspheres 59

5.6 SEM photographs of SLM floating microspheres 60

5.7 Average diameter of SLM floating microspheres 61

5.8 Frequency distribution of SLM floating microspheres 62

LIST OF FIGURES

LIST OF FIGURES

Department of pharmaceutics, Bharathi college of pharmacy

5.9 Standard calibration curve of SLM in methanol 64

5.10 Drug entrapment efficiency of SLM floating microspheres 65

5.11 Comparative in vitro release profile of SLM floating

microspheres

67

5.12 zero order release kinetics profile of Silymarin floating

microspheres 72

5.13 First order release kinetics profile of Silymarin floating

microspheres 72

5.14 Higuchi matrix diffusion release kinetics profile of Silymarin

floating microspheres 73

5.15 Peppas model release kinetics profile of Silymarin floating

microspheres 73

5.16 DSC Thermo gram of SLM 74

5.17 DSC thermogram of physical mixture of SLM, Hydroxy

propyl methyl cellulose E 50 LV and Ethyl cellulose 75

5.18 DSC Thermo gram of SLM floating microspheres 76

CHAPTER 1 INTRODUCTION

Department of pharmaceutics, Sarada Vilas college of pharmacy Page 1

1.1 NOVEL DRUG DELIVERY SYSTEM

The design of oral controlled DDS should be primarily aimed to achieve more

predictable and increased bioavailability. Now a day‟s most of the pharmaceutical

scientist is involved in developing the ideal DDS. This ideal system should have

advantage of single dose for the whole duration of treatment and it should deliver the

active drug directly at the specific site. Scientists have succeeded to develop a system

and it encourages the scientists to develop control release systems. Controlled release

implies the predictability and reproducibility to control the drug release, drug conc in

target tissue and optimization of the therapeutic effect of a drug by controlling its

release in the body with lower and less frequent dose.1 However, this approach is be

dilled with several physiological difficulties such as in ability to restrain and locate

the controlled drug delivery system within the desired region of the GIT due to

variable gastric emptying and motility. Furthermore, the relatively brief GET in

humans which normally average 2-3 hrs through the major absorption zone, i.e.,

stomach and upper part of the intestine can result in incomplete drug release from the

drug delivery system leading to reduced efficacy of the administered dose. Therefore,

control of placement of a DDS in a specific region of the GI tract offers advantages

for a variety of important drugs characterized by a narrow absorption window in the

GIT or drugs with a stability problem.2

Anatomy and physiology of stomach 3

The stomach is the most dilated part of the GIT and is situated between the

lower end of the oesophagus and the small intestine .Its opening to the duodenum is

1. INTRODUCTION



controlled by the pyloric sphincter .The stomach can be divided into four anatomical

regions, namely the fundus, the body, the antrum and the pylorus.

Fig 1.1 Anatomy of stomach

The two major functions of the stomach are

To act as a temporary reservoir for ingested food and to deliver it to the

duodenum at a controlled rate.

To reduce the ingested solids to uniform creamy consistency, known as chime, by

the action of acid and enzymatic digestion. This enables better contact of the

ingested material with the mucous membrane of the intestines and their by

facilitates absorption.

Another perhaps less obvious, function of stomach is its role in reducing the

risk of noxious agents reaching intestine.



Gastric motility

Gastric emptying occurs during fasting as well as fed states. During the fasting

state an interdigestive series of electrical events take place, which cycles through

stomach and intestine every 2 to 3 hrs. This is called the interdigestive myloelectric

cycle or migrating myoelectric cycle (MMC), which is further divided into 4 phases

as described by Wilson and Washington.4, 5

Phase I (basal phase) lasts from 40 to 60 min with rare contractions.

Phase II (preburst phase) lasts for 40 to 60 min with intermittent action and potential

contractions. As the phase progresses the intensity and frequency also increases

gradually.

Phase III (burst phase) lasts for 4 to 6 min. It includes intense and regular contractions

for short period. It is due to this wave that all the undigested material is swept out of

the stomach down to the small intestine. It is also known as the housekeeper wave.

Phase IV lasts for 0 to 5 min and occurs between phases III and I of 2 consecutive

cycles.

After the ingestion of a mixed meal, the pattern of contractions, changes from

fasted to that of fed state. This is also known as digestive motility pattern and

comprises continuous contractions as in phase II of fasted state. These contractions

result in reducing the size of food particles (to less than 1 mm), which are propelled

toward the pylorus in a suspension form. During the fed state onset of MMC is

delayed resulting in slowdown of gastric emptying rate. Scintigraphic studies

determining gastric emptying rates revealed that orally administered controlled

release dosage forms are subjected to basically two complication, that of short gastric

residence time and unpredictable gastric emptying rate.6, 7



Criteria for selection of drug candidate for GRDDS 8

The GRDDS are suitable for following types of drug therapy

Absorption from upper GIT, drugs have a particular site for maximum absorption

eg. Ciprofloxacin, whose maximum absorption is in the stomach only. The

absorption of Metformin hydrochloride is confirmed to small intestine only and

the conventional sustained release dosage forms may have poor bioavailability

since absorption appears to diminish when the dosage form pass in to large

intestine.

Drugs having low PKa

, which remains unionized in stomach for better absorption.

Drugs having reduced solubility at higher pH eg. Captopril and Chlordiazepoxide

and the bioavailability of drugs that get degraded in alkaline pH can be increased

by formulating gastro-retentive dosage forms eg. Doxifluridine, which degrades in

small intestine.

Local action as it is seen in the treatment of H. Pylori by Amoxicillin and

Misoprostol for ulcers.

To minimize gastric irritation that may be caused by sudden increase of drug

concentration in the stomach eg. NSAIDs.

Improve effectiveness of particular drugs eg. Antibiotics in the colon tend to

disturb the micro flora causing overgrowth of micro organisms like Clostridium

difficile causing colitis.

Factors affecting gastro retentive system

The GRT of dosage forms is controlled by several factors such as density and

size of the dosage form, food intake, nature of the food, posture, age, gender, sleep

and disease state of the individual (eg. Crohn‟s disease and diabetes) and

administration of drugs such as prokinetic agents (Mosapiride and Metoclopramide). 9



Density of dosage form

Dosage forms having a density lower than that of gastric fluid experience

floating behavior and hence gastric retention. A density of <1.0 gm/cm3 is required to

exhibit floating property. However, the floating tendency of the dosage form usually

decreases as a function of time, as the dosage form gets immersed into the fluid, as a

result of the development of hydrodynamic equilibrium.10

Size and shape

Dosage form unit with a diameter of more than 7.5 mm are reported to have an

increased GRT competed to with those with a diameter of 9.9 mm. The dosage form

with a shape tetrahedron and ring shape devises with a flexural modulus of 48 and

22.5 KSI are reported to have better GIT at 90 to 100 % retention for 24 hrs

compared with other shapes.11

Fed or unfed state

Under fasting conditions, the GI motility is characterized by periods of strong

motor activity or the MMC that occurs every 1.5 to 2 hrs. The MMC sweeps

undigested material from the stomach and if the timing of administration of the

formulation coincides with that of the MMC, the GRT of the unit can be expected to

be very short. However, in the fed state, MMC is delayed and GRT is considerably

longer.12

Nature of the meal

Feeding of indigestible polymers of fatty acid salts can change the motility

pattern of the stomach to a fed state, thus decreasing the GER and prolonging the

drug release.13



Caloric content

GRT can be increased between 4 to 10 hrs with a meal that is high in proteins

and fats.

Frequency of feed

The GRT can increase by over 400 min when successive meals are given

compared with a single meal due to the low frequency of MMC.14

Effect of gender, posture and age

Females showed comparatively shorter mean ambulatory GRT than males,

and the gastric emptying in women was slower than in men.15

The floating and non-floating systems behaved differently. In the upright

position, the floating systems floated to the top of the gastric contents and remained

for a longer time, showing prolonged GRT. But the non-floating units settled to the

lower part of the stomach and underwent faster emptying as a result of peristaltic

contractions, and the floating units remained away from the pylorus.16

However, in

supine position, the floating units are emptied faster than non-floating units of similar

size.17

1.2 APPROACHES TO GASTRIC RETENTION

A number of approaches have been used to increase the GRT of a dosage form

in stomach by employing a variety of concepts. These include

Floating systems 18

FDDS have a bulk density lower than gastric fluids and thus remain buoyant

in the stomach for a prolonged period of time, without affecting the GER. While the

system is floating on the gastric contents, the drug is released slowly at a desired rate

from the system. After the release of the drug, the residual system is emptied from the

stomach. These results in an increase in the GRT and a better control of fluctuations



in the plasma drug concentration. Floating systems can be classified into two distinct

categories, effervescent and non-effervescent systems.

Bio/Muco-adhesive systems 19

Bio adhesive or mucoadhesive systems are used to localize a delivery device

within the lumen and cavity of the body to enhance the drug absorption process in a

site-specific manner. The approaches involve the use of bio adhesive polymers that

can be adhering to the epithelial surface of the GIT. The proposed mechanism of bio

adhesive is the formation of hydrogen and electrostatic bonding at the mucus polymer

boundary.

Swelling and expanding systems 20, 21

These are the dosage forms, which after swallowing; swell to an extent that

prevents their exit from the pylorus. As a result, the dosage form is retained in the

stomach for a longer. These systems may be named as “plug type system” since they

exhibit the tendency to remain logged at the pyloric sphincter if that exceed a

diameter of approximately 12-18 mm in their expanded state. Such polymeric

matrices remain in the gastric cavity for several hrs even in the fed state.

A balance between the extent and duration of swelling is maintained by the

degree of cross-linking between the polymeric chains. A high degree of cross-linking

retards the swelling ability and maintains its physical integrity for prolonged period.

High density systems 22

These systems with a density of about 3 g/cm3 are retained in the rugae of the

stomach and are capable of withstanding its peristaltic movements. A density of 2.6-

2.8 g/cm3

acts as a threshold value after which systems can be retained in the lower

part of the stomach. High-density formulations include coated pellets. Coating is done



by heavy inert materials such as barium sulphate, zinc oxide, titanium dioxide, and

iron powder.

Incorporation of passage delaying food agents 23

Food excipients like fatty acids eg. Salts of myristic acid change and modify

the pattern of the stomach to a fed state, thereby decreasing GER and permitting

considerable prolongation of release. The delay in the gastric emptying after meals

rich in fats is largely caused by saturated fatty acids with chain length of C10-C14.

Ion exchange resins 24

A coated ion exchange resin bead formulation has been shown to have gastric

retentive properties, which was loaded with bicarbonates. Ion exchange resins are

loaded with bicarbonate and a negatively charged drug is bound to the resin. The

resultant beads were then encapsulated in a semi-permeable membrane to overcome

the rapid loss of carbon dioxide. Upon arrival in the acidic environment of the

stomach, an exchange of chloride and bicarbonate ions take place, as a result of this

reaction carbon dioxide was released and trapped in the membrane thereby carrying

beads towards the top of gastric content and producing a floating layer of resin beads

in contrast to the uncoated beads, which will sink quickly.

Osmotic regulated systems 25

It is comprised of an osmotic pressure controlled drug delivery device and an

inflatable floating support in a bio erodible capsule. In the stomach the capsule

quickly disintegrates to release the Intragastric osmotically controlled drug delivery

device. The inflatable support inside forms a deformable hollow polymeric bag that

contains a liquid that gasifies at body temperature to inflate the bag. The osmotic

controlled drug delivery device consists of two components, drug reservoir

compartment and osmotically active compartment.



Fig 1.2 Classification of gastro retentive drug delivery

1.3 FLOATING DRUG DELIVERY SYSTEMS (FDDS)

Based on the mechanism of buoyancy, two distinctly different technologies

have been utilized in the development of FDDS, which are effervescent system and

non- effervescent system.

Effervescent system 26, 27, 28

Effervescent systems include use of gas generating agents, carbonates

(Sodium bicarbonate) and other organic acid (Citric acid and Tartaric acid) to produce

carbon dioxide (CO2) gas, thus reducing the density of the system and making it to

float on the gastric fluid. These effervescent systems further classified into two types

Gas generating systems

Intra gastric single layer floating tablet or Hydro dynamically balanced system

(HBS)



Fig 1.3 Hydro dynamically balanced system

These are formulated by mixing the CO2 generating agents and the drug

within the matrix tablet (Fig1.3). These have a bulk density lower than gastric fluids

and therefore remain floating in the stomach unflattering the GER for a prolonged

period. The drug is slowly released at a desired rate from the floating system and after

the complete release the residual system is expelled from the stomach. This leads to

an increase in the GRT and a better control over fluctuations in plasma drug

concentration.

Intra gastric bilayered floating tablets

These are also compressed tablet and contain two layers for:

Immediate release layer and

Sustained release layer (Fig.1.4).



Fig 1.4 Intra gastric bilayer floating tablet

Multiple unit type floating pills

These systems consist of sustained release pills as „seeds‟ surrounded by

double layers. The inner layer consists of effervescent agents while the outer layer is

of swellable membrane layer. When the system is immersed in dissolution medium at

body temperature it sinks at once and then forms swollen pill like balloon and float as

the density decreases (Fig1.5 and 1.6).

Fig 1.5 A multi-unit type oral floating dosage system



Fig 1.6 Stages of floating mechanism

A. Penetration of water

B. Generation of CO2 and floating

C. Dissolution of drug

Intra gastric floating gastrointestinal drug delivery system

This system can be made to float in the stomach because of floatation

chamber, which may be a vacuum or filled with air or a harmless gas, while drug

reservoir is encapsulated inside a microporus compartment (Fig1.7).

Fig 1.7 Intra gastric floating gastrointestinal drug delivery device



Inflatable gastrointestinal delivery systems

In these systems an inflatable chamber is incorporated, which contains liquid

that gasifies at body temperature to cause the chamber to inflate in the stomach.

These systems are fabricated by loading the inflatable chamber with a drug reservoir,

which can be a drug, impregnated polymeric matrix, then encapsulated in a gelatin

capsule. After oral administration the capsule dissolves to release the drug reservoir

together with the inflatable chamber. The inflatable chamber automatically inflates

and retains the drug reservoir compartment in floating position. The drug

continuously released from the reservoir into the gastric fluid (Fig 1.8).

Fig 1.8 Inflatable gastrointestinal delivery system

Intragastric osmotically controlled drug delivery system

It is comprised of an osmotic pressure controlled drug delivery device and an

inflatable floating support in a biodegradable capsule. In the stomach capsule quickly

disintegrates to release the intragastric osmotically controlled drug delivery device.



The inflatable support inside forms a deformable hollow polymeric bag that contains

a liquid that gasifies at body temperature to inflate the bag. The osmotic pressure

controlled drug delivery device consists of two components; drug reservoir

compartment and an osmotically active compartment.

The drug reservoir compartment is enclosed by a pressure responsive

collapsible bag, which is impermeable to vapour and liquid and has a drug delivery

orifice. The osmotically active compartment contains an osmotically active salt and is

enclosed within a semi permeable housing. In the stomach, the water in the GI fluid is

continuously absorbed through the semi permeable membrane into osmotically active

compartment to dissolve the osmotically active salt. An osmotic pressure is thus

created which acts on the collapsible bag and turns in forces the drug reservoir

compartment to reduce its volume and activate the drug reservoir compartment to

reduce its volume and activate the drug release in solution form through the delivery

orifice (Fig.1.9).

Fig 1.9 Intra gastric osmotically controlled drug delivery system



Non effervescent systems 29, 30

The Non effervescent FDDS is based on mechanism of swelling of polymer or

bioadhesion to mucosal layer in GI tract. The most commonly used excipients in non-

effervescent FDDS are gel forming or highly swellable cellulose type hydrocolloids,

polysaccharides and matrix forming materials such as polycarbonates, polyacrylates,

polymethacrylates, polystyrenes etc. and bioadhesive polymer such as chitosan and

carbopol. The various types of these systems are

Single layer floating tablets

They are formulated by intimate mixing of drug with a gel-forming

hydrocolloid, which swells in contact with gastric fluid and maintain bulk density of

less than unity. The air trapped by the swollen polymer confers buoyancy to these

dosage forms.

Alginate beads

Multi unit floating dosage forms were developed from freeze-dried calcium

alginate. Spherical beads of approximately 2.5 mm diameter can be prepared by

dropping a sodium alginate solution into aqueous solution of calcium chloride,

causing precipitation of calcium alginate leading to formation of porous system,

which can maintain a floating force for over 12 hrs. These floating beads gave a

prolonged residence time of more than 5.5 hrs.

1.4 FLOATING MICROSPHERES

Multiple-unit floating (hollow) microspheres by emulsion solvent diffusion

technique were prepared with Drug and acrylic polymer. These were dissolved in an

ethanol-dichloromethane mixture, and poured into an aqueous solution of PVA with

stirring to form emulsion droplets. The rate of drug release in micro balloons was

controlled by changing the polymer to drug ratio. Microbaloons were floatable in



vitro for 12 hrs when immersed in aqueous media. Radio graphical studies proved

that microbaloons orally administered to humans were dispersed in the upper part of

stomach and retained there for 3 hrs against peristaltic movements.

Low density system / floating drug delivery system (FDDS)

Low density system have a bulk density less than gastric fluids and so remain

buoyant in the stomach without affecting the gastric emptying rate for a prolonged

period of time. While the system is floating on the gastric contents, the drug is

released slowly at the desired rate.31

Fig 1.10 Intragastric floating microbaloons drug delivery system

These are made of the low density materials because of low density core these

are called microbaloons. The low density materials used in this method of preparation

are Polycarbonate, Eudragit S, cellulose acetate, calcium alginate; agar and low

methoxylated pectin are commonly used as polymers.32

Advantages of FDDS 33

The gatroretentive systems are advantageous for drugs absorbed through the

stomach eg. Ferrous salts, antacids.



Acidic substances like aspirin cause irritation on the stomach wall when come in

contact with it. Hence HBS formulation may be useful for the administration of

aspirin and other similar drugs.

Administration of prolongs release floating dosage forms, tablet or capsules, will

result in dissolution of the drug in the gastric fluid. They dissolve in the gastric

fluid would be available for absorption in the small intestine after emptying of the

stomach contents. It is therefore expected that a drug will be fully absorbed from

floating dosage forms if it remains in the solution form even at the alkaline pH of

the intestine.

The gatroretentive systems are advantageous for drugs meant for local action in

the stomach eg. Antacids.

When there is a vigorous intestinal movement and a short transit time as might

occur in certain type of diarrhea, poor absorption is expected. Under such

circumstances it may be advantageous to keep the drug in floating condition in

stomach to get a relatively better response.

Disadvantages of FDDS

Floating system is not feasible for those drugs that have solubility or stability

problem in GIT.

These systems require a high level of fluid in the stomach for drug delivery to

float and work efficiently.

The drugs that are significantly absorbed through out gastrointestinal tract, which

undergo significant first pass metabolism, are only desirable candidate.

Some drugs present in the floating system causes irritation to gastric mucosa.



APPLICATIONS 34, 35, 36

Sustained drug delivery

Hydrodynamically balanced system can remain in the stomach for long

periods and hence can release the drug over a prolonged period of time. The problem

of short gastric residence time encountered with an oral controlled release

formulation, hence, can be overcome with these systems. These systems have bulk

density of <1, as a result of which they can float on the gastric contents. Recently

sustained release floating capsules of nicardipine were developed and evaluated in

vivo. The formulation compared with commercially available MICARD capsules

using rabbits. Plasma conc time curves showed a longer duration for administration

(16 hrs) in the sustained release floating capsules as compared with conventional

MICARD cap (8 hrs).

Site specific drug delivery

These systems are particularly advantages for drugs that are specifically

absorbed from stomach or the proximal part of the small intestine eg. Riboflavin,

Furosemide and Misoprostal.

A bilayer floating capsule was developed for local delivery of Misoprostol,

which is a synthetic analog of Prostaglandin E, used as protectant of gastric ulcer

caused by administration of NSAIDs. By targeting slow delivery of misoprostol to the

stomach, desired therapeutic level could be achieved and drug waste could be

reduced.

Absorption enhancement

Drugs that have poor bioavailability because of site specific absorption from

the upper part of the GIT are potential candidates to be formulated as FDDS, thereby

maximizing their absorption. A significant increase in the bioavailability of floating



dosage forms (42.9%) could be achieved as compared with commercially available

LASIX tablet (33.4%) and enteric coated LASIX-long product (29.5%).

Maintenance of constant blood level

These systems provide an easy way of maintaining constant blood level with

an ease of administration and better patient compliance.

Limitations 37

The floating system requires a sufficiently high level of fluid in the stomach for

the system to float. This problem can be overcome by coating the dosage form

with bio adhesive polymer which adhere to gastric mucosa or administering

dosage form with a glass full of water (200-250 ml).

Floating system is not suitable for drugs that have stability or solubility problem

in gastrointestinal fluid or that irritate gastric mucosa. Drugs which have multiple

absorption site or which undergo first pass metabolism were not desirable

candidate for FDDS.

The single unit floating dosage form is associated with “all or none concept”.

This problem can be overcome by formulating multiple unit system like floating

microsphere or microballons.

Floating dosage form should not be given to the patients just before going to the

bed as gastric emptying occurs rapidly when the subject remains in supine

posture.



Marketed products of floating drug delivery system 38

Table 1.1 Marketed products of floating drug delivery system

Sl no

Product

Drug (dose)

Delivery

system

Company,

Country

1

Madopar

Levodopa (100mg)

Benserzide(25mg)

Floating,

CRCapsule

Roche Products,

USA

2

Valrelease

Diazepam (15mg)

Floating

liquid alginate

preparation

Hoffmann

laRoche, USA

3

Topalkan

Al -Mg antacid

Floating

dosage form

Pierre Fabre drug,

France

4

Cifran OD

Ciprofloxacin(1g)

Gas

generating

floating form

Ranbaxy India

5 Liquid

gavison

Al hydroxide(95mg)

Mg

carbonate(358mg)

preparation

Colloidal gel

forming

GlaxoSmithKline,

India

6

Conviron

Ferrous sulphate

FDDS

Ranbaxy India

7 Liquid

gavison

Al hydroxide(95mg)

Mg

carbonate(358mg)

preparation

Colloidal gel

forming

Glaxosmithkline,

India

8 Almagate

Flat coat

Al -Mg antacid

Effervescent

floating liquid

alginate

Pierre Fabre drug,

France



1.5 LIVER 39

The liver plays an astonishing array of vital functions in the maintenance,

performance and regulating homeostasis of the body. Liver is considered to be one

of the most vital organs that functions as a centre of metabolism for nutrients such

as carbohydrates, proteins and lipids and excretion of waste metabolites.

Additionally, it is also handling the metabolism the biochemical pathways to

growth, fight against disease, nutrient supply, energy provision and reproduction

and excretion of drugs and other xenobiotics from the body thereby providing

protection against foreign substances by detoxifying and eliminating them. The

bile secreted by the liver has, among other things, plays an important role in

digestion. Enhanced lipid per oxidation during metabolism of ethanol may result

in development of hepatitis leading to cirrhosis. Since time immemorial, mankind

has made the use of plants in the treatment of various ailments. The Indian

Traditional Medicine like Ayurvedic, Siddha and Unani are predominantly based

on the use of plant materials. Herbal drugs have gained importance and popularity

in recent years because of their safety, efficacy and cost effectiveness. The

association of medical plants with other plants in their habitat also influences their

medicinal values in some cases. One of the important and well -documented uses

of plant -products is their use as hepatoprotective agents. Hence, there is an ever

increasing need for safe hepatoprotective agent.

TREATMENT OF LIVER DISEASE:

Each liver disease will have its own specific treatment regimen. For example,

Hepatitis A requires supportive care to maintain hydration while the body's

immune system fights and resolves the infection. Patients with gallstones may

require surgery to remove the gallbladder.

Other diseases may need long-term medical care to control and minimize the

consequences of their disease. In patients with cirrhosis and end-stage liver

disease, medications may be required to control the amount of protein

absorbed in the diet. The liver affected by cirrhosis may not be able to

metabolize the waste products, resulting in elevated blood ammonia levels and



hepatic encephalopathy. Low sodium diet and water pills (diuretics) may be

required to minimize water retention.

In those with large amounts of as cites fluid, the excess fluid may have to be

occasionally removed with a needle and syringe (paracentesis). Using local

anaesthetics, a needle is inserted through the abdominal wall and the fluid

withdrawn. Operations may be required to treat portal hypertension and

minimize the risk of bleeding. Liver is the final option for patients whose liver

has failed.

CLASSIFICATION OF HEPATOPROTECTIVE DRUGS :

These are generally classified into 3 categories without any strict delineation amongst

them.

Anti Hepatotoxic agents: These generally antagonize the effects of any

hepatotoxins causing hepatitis or any liver disease.

Hepatotropic agents: These generally support or promote the healing process

of the liver. In practice these two activities cannot be easily distinguished from

each other.

Hepatoprotective agents: These generally prevent various types of liver

affections prophilactically. In general any hepatoprotective agent can act as an

anti hepatotoxic or hepatotropic agent but the vice versa is always not true.

In the present work Silymarin (SLM) was chosen as the drug to be

incorporated into the polymers like HPMC E50 LV and EC. It is one of the most

powerful drug for the hepatic diseases. SLM stimulates synthesis of polymerase ,

enhances ribosomal protein synthesis and exerts a membrane stabilizing effect.

SLM also reduces prostaglandin Synthesis. SLM is known for its hepatoprotective

action against hepatic glutathione depletion induced by ethyl alcohol and paracetamol

in animal studies.



SLM reduces the turnover of membrane phospholipids and stabilises both extra and

intracellular membranes inside hepatocytes. SLM also increases the phagocytic

activity of the Kupffer cells, contributing to hepatoprotective and regenerative effects.

.The aim of the work is to develop the floating of SLM and it has the short biological

is half life is 3 to 4 hr and it has two pKa values 6.8 and 6.2.

The SLM is degraded as the pH increases so it is necessary to dissolve in the

less pH for the protection of the drug and to reduce the gastric disturbance and more

over, the site of absorption of SLM is in the stomach pH. Hence it is suitable to

formulate the SLM as floating microspheres to reduce frequency of dosing and to

prevent the drug from degradation in the intestinal pH.

CHAPTER 2 AIMS AND OBJECTIVES


Gastro retentive systems can remain in the gastric region for several hours and

hence significantly prolong the GRT of drugs. Prolonged gastric retention improves

bioavailability, reduces drug waste and improves solubility of drugs that are less

soluble in a high pH environment. It has applications also for local drug delivery to

the stomach and proximal small intestine. Gastro retention helps to provide better

availability of new products with new therapeutic possibilities and substantial

benefits for patients.30

SLM has a half life of (4-6 hrs) and it reaches a peak plasma concentration after 1hr.

It is highly soluble in 0.1M HCL (11.803 mg/ml) and solubility decreases with

increasing pH over the physiological range which makes SLM a suitable candidate

for FDDS in order to prolong the GRT. 38, 39

In this present investigation it was proposed.

To formulate SLM floating microspheres using polymers like HPMC E 50 LV and

EC for controlled delivery of Hepatoprotective drug SLM.

To evaluate the polymer characteristics and SLM floating microsphere

characteristics.

To study the effect of polymer concentration on SLM floating microsphere

characteristics.

To evaluate physico-chemical characteristics like drug interaction study (FTIR),

surface morphology (SEM), mean particle size, and size distribution etc.

To evaluate the drug entrapment efficiency of the formulations.

To perform in vitro dissolution studies.

2. AIMS AND OBJECTIVES

CHAPTER 2 AIMS AND OBJECTIVES


To evaluate the release kinetics.

To confirm the physical state of drug in the prepared SLM floating microspheres

by using DSC.

2.1 PLAN OF WORK

Preformulation studies

Solubility

Melting point

UV spectroscopy

Preparation studies

Preparation of SLM floating microspheres using polymers like HPMC E 50 LV

and EC for Controlled drug delivery.

Evaluation studies

Drug interaction study (FTIR)

Surface morphology (SEM)

Particle size distribution of prepared SLM floating microspheres

Drug entrapment efficiency

In vitro dissolution studies

Kinetics of dug release

Physical state of SLM in floating microspheres (DSC)

CHAPTER 3 REVIEW OF LITERATURE


Yuveraj Singh et al., 7 studied the floating microspheres of Verapamil Hydrochloride

for improving the drug bioavailability by prolongation of gastric residence time by

using polymers such as cellulose acetate, acrycoat S100 and eudragit S100. The

prepared microspheres exhibited prolong buoyant for more than 12 hrs.

Gattani YS et al.,8 formulated and evaluated the controlled release system for

Aceclofenac to increase its residence time in the stomach without contact with the

mucosa, achieved through the preparation of floating microparticles by the

emulsification solvent-evaporation technique consisting of eudragit RS 100 as a

polymer. The prepared microspheres exhibited prolonged drug release (> 12hrs) and

remained buoyant for > 12 hrs.

Srivastava AK et al.,15

studied the floating microsphere of Cimetidine by solvent

evaporation method using polymers of hydroxylpropylmethyl cellulose and ethyl

cellulose. The prepared microspheres exhibited prolonged drug release (~8 hrs) and

remained buoyant for > 10 hrs. The mean particle size increased and the drug release

is decreased at higher polymer concentration.

Fursule RA et al.,17

formulated and evaluated oil entrapped floating gel beads of

Amoxicillin Trihydrate prepared by using sodium alginate as gelling agent, the

entrapped gel beads can be used as floating drug delivery system for local as well as

systemic drug delivery.

Kumaresh SS et al. 18

studied the effect of co excipients on drug release and floating

property of Nifedipine hollow microspheres and they developed by incorporating the

drug in cellulose acetate hollow microspheres by solvent diffusion-evaporation

3. REVIEW OF LITERATURE



technique in presence of coexcipient. The percentage buoyancy followed the rank

order of blank (no coexcipient) > dibutyl phthalate > polyethylene glycol > poly (ε-

caprolactone) after 15 hrs of floating. Release of Nifedipine was enhanced by the

addition of coexcipients.

Jain AK et al.,21

formulated Famotidine floating microspheres by solvent evaporation

method using polymer acrycoat S100 and cellulose acetate. The microspheres exhibit

prolonged drug release (18 hrs) and remain buoyant for more than 12 hrs.

Basavaraj B.V et al. 22

studied micro balloons loaded with drug Diclofenac Sodium

in their outer polymer shells by novel emulsion solvent diffusion. The ethanol:

dichloromethane solution of drug and eudragit-S were poured into an aqueous

solution of PVA that was thermally controlled at 40

C. The gas phase generated in the

dispersed polymer droplet by the evaporation of solvent formed an internal cavity in

the microsphere of the polymer with the drug. The microspheres continuously float

for more than 12 hrs in the acidic medium.

Klausner A et al.,26

were prepared microbaloons by the emulsion-solvent diffusion

method using drug Tranilast and acrylic polymer. The drug release profiles from

microbaloons exhibited enteric behavior. The release rate was controlled by changing

the ratio of polymer to drug in the microbaloons. Most of the microbaloons were

floatable in vitro even testing for 12 hrs when immersed in aqueous media, owing to

their low particle density (less than unity).

Sunil KJ et al.,34

studied on porous carrier-based floating Orlistat

microspheres for gastric delivery. Calcium silicate is used as porous carrier and

eudragit S as polymer. Floating microspheres of Orlistat prepared by the solvent

evaporation method, the microspheres found to be regular in shape and highly porous.



The microspheres containing 200 mg calcium silicate showed the best floating ability

(88% buoyancy) in simulated gastric fluid.

Chavanpatil M et al.,40

developed Ofloxacin sustained release floating oral delivery

system in order to prolong the gastric retention time. Different polymers such as

psyllium husk, HPMC K100M, crospovidone were used. It was found that

dimensional stability of the formulation increases with the increasing psyllium husk

concentration and also in vitro drug release rate increased with increasing amount of

crospovidone.

Srivastava AK et al.,47

prepared floating microspheres of Cimetidine by solvent

evaporation method using polymers HPMC and ethyl cellulose. In vitro drug release

studies showed that the prepared microspheres exhibited prolonged drug release

(~8hrs) and remained buoyant for more than 10 hrs.

Nikhil Gupta et al.,48

studied the tensile properties of glass microbaloons of

epoxy resin syntactic foams. Four types of glass microbaloons, having 220, 320, 380

and 460 kg/m3 density, are used with epoxy resin matrix for making the syntactic

foam samples. These foams contain 30%, 40%, 50% and 60% microbaloons by

volume. The foams containing low strength microbaloons showed lower tensile

modulus compared to that of the neat resin but the presence of high strength

microbaloons lead to an increase in the tensile modulus of the composites.

Deepa MK et al.,49

formulated the Cefedoxime Proxetil floating microspheres by

non-aqueous solvent evaporation method using polymers such as hydroxyl propyl

methyl cellulose (HPMC K 15 M), ethyl cellulose in different ratios of Cefpodoxime

Proxetil formulation. The best drug release profiles were seen with formulation at the

ratio of drug to polymer was 1:2.



Sahoo SK et al.,50

studied floating microspheres of Ciprofloxacin Hydrochloride. The

microspheres were prepared by simple dripping method by using sodium alginate and

hydroxy propyl methyl cellulose (HPMC) as a carrier, Sodium bicarbonate was used

as the gas forming agent and 1% calcium chloride solution containing 10% acetic acid

for carbon dioxide release and gel formation. The enhanced buoyancy and controlled

release properties of sodium bicarbonate containing microspheres made them an

excellent candidate for floating drug dosage form.

Madhavi BB et al.,51

developed a new class of antidepressants its higher solubility in

water results in burst effect with sudden peak levels of drug in blood. The half lives of

Venlafaxine Hydrochloride (VEN). The microbeads were prepared by the ionotropic

gelation of sodium alginate in calcium chloride solution. The method had resulted in

good encapsulation efficiency and micron sized alginate spheres. The drug release

was found to be sustained for 16 hrs and was found to follow the Korsemeyer Peppas

kinetics.

Narendra C et al.,52

developed bilayer floating tablet of Metoprolol Tartarate using

different ratio of HPMC K4M and HPMC K10M cp, SCMC and PVP K30. Tablets

were studied for in vitro dissolution studies, buoyancy determination, floating time. It

showed that increase in conc of both HPMC K4M and HPMC K100M increase

floating time and SCMC is required in formulation to maintain the integrity of tablet.

Jain SK et al.,53

prepared porous carrier based floating granular delivery system of

Repaglinide using calcium silicate as porous carrier, HPMC K4M, ethyl cellulose and

carbopol 940 as matrix forming polymers and evaluated for its gastro-retentive and

controlled release properties, particle morphology, micromeritic properties, in vitro

floating behaviour, drug content (%), in vitro drug release, comparison with marketed

capsule and in vivo study in albino rat.



Joseph NJ et al.,54

developed floating type dosage form (FDF) of Piroxicam in

hollow polycarbonate (PC) microspheres capable of floating on simulated gastric and

intestinal fluids was prepared by a solvent evaporation technique. Incorporation

efficiencies of over 95% were achieved for the encapsulation. In vitro release of

Piroxicam from PC microspheres into simulated gastric fluid at 37oC showed no

significant burst effect. The amount released increased with time for about 8 hrs after

which very little was found to be released up to 24 hrs.

Guerrero S et al.,55

prepared Ketotifen (KT)-loaded chitosan microspheres (MS) for

controlled release delivery systems. Microspheres were prepared by a spray-drying

technology followed by treating with glutaraldehyde solutions in methanol as cross-

linker. Results showed that very small spherical microspheres with a high load of KT

were obtained. KT loading decreased with cross-linking .Interactions between KT and

chitosan avoided total KT release from cross-linked MS. After intraperitoneal (i.p.)

administration, microsphere aggregations were adhered to muscle subjacent to the

tegument and to adipose tissue, and there were no evident sings of rejection; KT was

detected in blood stream (0.37–0.25 l g/ml) at 24 hrs, which was longer than the i.p.

administration of the drug in solution (39.4 l g/ml at 24 hrs).

Muzzarellia C et al.,56

prepared chitosan-polyuronan microspheres, in which chitosan

were used as cationic polymer and alginic acid, polygalacturonic acid, carboxymethyl

cellulose, carboxymethyl guaran, acacia gum, 6-oxychitin, xanthan, hyaluronic acid,

pectin, k-carrageenan, and guaran as an ionic polymer. Those made of chitosan–

xanthan or chitosan–guaran was unexpectedly found to be soluble in water; similarly,

the chitosan–pectin microspheres were almost soluble. The microspheres containing

hyaluronic acid or k-carrageenan underwent swelling when contacted with water; the

other ones were insoluble. The microspheres were characterized by FTIR, X-ray



diffraction spectrometry and scanning electron microscopy. The structural alterations

detected were mainly due to interactions between the amino groups and the carboxyl

groups.

Li S et al.,58

studied the effect of HPMC (different viscosity grades) and carbopol

934P on the release and floating properties of gastric drug delivery system carried out

using factorial design. The study concluded that polymer with lower viscosity was

found to be beneficial than the higher viscosity grades of HPMC type in improving

the floating properties and incorporation of carbopol however was found to

compromised the floating capabilities and release rate of active drug, which might be

due to difference in the basic properties of three polymers due to their water uptake

potential and functional group substitution.

Sawicki W et al.,69

prepared Verapamil Hydrochloride (VH) floating pellets using

kollicoat SR 30 D as a coating agent and 10% plasticizers like propylene glycol,

triethyl citrate and dibuthyl sebecate. Two kinds of cellulose, microcrystalline and

sodium hydrocarbonate were the main components of pellet core. Tablets were

evaluated as regards to effect of upper punch compression force on mechanical

strength, friability and floatation starting time. It was proved that increasing

compression force contributed to greater hardness, lower friability, lower release and

delayed start of floatation time.

Sriamornsak P et al.,60

prepared Metronidazole emulsion gel beads using calcium

pectinate by emulsion-gelation method. It was found that increasing drug to pectin

ratio in the beads slowed the drug release from the conventional and EMG beads. The

result suggests the release behaviour of EMG beads could be modified by hardening

with 2% glutaraldehye or by coating with eudragit RL.



Rao, MR et al.,61

developed Rosiglitazone maleate microspheres by solvent

diffusion–evaporation. A full factorial design was applied to optimize the formulation.

The results of 32 full factorial design revealed that the conc of ethyl cellulose 7 cps

(X1) and stirring speed (X2) significantly affected drug entrapment efficiency,

percentage release after 8 hrs and particle size of microspheres.

Senthilkumar SK et al.,63

developed floating microsphere using Rabeprazole Sodium

(RS) as a model drug for prolongation of the gastric retention time. The microspheres

were prepared by the solvent evaporation method using different polymers like

hydroxy propyl methyl cellulose and methyl cellulose. The average diameter and

surface morphology of the prepared microsphere were characterized by optical

microscope and scanning electron microscopic methods respectively. In vitro drug

release studies were performed and the drug release kinetics was evaluated using

linear regression method. The effect of various formulation variables on the size and

drug release was investigated.

Barhate SD et al.,64

developed multiparticulate gastro retentive drug delivery system

of Ketorlac Trometamol. The gastro retentive drug delivery system can be prepared to

improve the absorption and bioavailability of ketorlac Trometamol by retaining the

system in to the stomach for prolonged period of time. The floating drug delivery

system of Ketorlac Trometamol was prepared by emulsion solvent diffusion method

by using ethyl cellulose, HPMC K4M, Eudragit R 100, Eudragit S 100 polymers in

varying concentration. The optimized formulation shows good buoyancy and In vitro

controlled release of Ketorlac Trometamol.

Dalwadisonali, et al.,82

.studied the influence of preparation methodology of silymarin

soild dispersion by using HPMC E15LV and it was investigated that the method

proved the best dissolution compared to pure drug.



K. Mallikarjuna Rao et al.,83

worked on the preparation and evaluation of floating

microspheres with Amoxicillin trihydrate as model drug for prolongation of gastric

residence time. The microspheres were prepared by the Non Aqueous solvent

diffusion method using polymers hydroxy propylmethyl cellulose and ethyl cellulose.

The compatibility studies between the drug and polymer was observed by using the

FTIR Analysis. The shape and surface morphology of prepared microspheres was

characterized by optical and scanning electron microscopy, respectively. In vitro drug

release studies were performed, and drug release kinetics were evaluated using the

linear regression method. The prepared microspheres exhibited prolonged drug

release (10 h) and remained buoyant for > 12 h. The mean particle size increased and

the drug release rate decreased at higher polymer concentration. In vitro studies

demonstrated super case II transport diffusion from the microspheres. By the

observation of all formulations results we concluded that formulation XIII having the

better drug release.

Rajeev Garg et al.,84

studied on cellulose microspheres – formulated with

hydroxylpropyl methylcellulose (HPMC) and ethyl cellulose (EC) – and eudragit

microspheres – formulated with Eudragit® S 100 (ES) and Eudragit® RL (ERL) -

were prepared by an emulsion-solvent evaporation method. The floating microspheres

were evaluated for flow properties based on parameters such as angle of repose and

compressibility index, as well as for various other physicochemical properties

including particle size, incorporation efficiency, in vitro floatability, and in vitro drug

release. The shape and surface morphology of the microspheres were characterised by

optical and scanning electron microscopy. Mean particle size increased while drug

release rate decreased with increasing EC and ES contents of cellulose and Eudragit

microspheres, respectively. Scanning electron microscopy showed pores on the



surface and interior of the microspheres. The microspheres exhibited prolonged drug

release for 12 h while still remained buoyant. Drug release kinetics, evaluated using

the linear regression method, followed Higuchi kinetics and drug release mechanism

was of the non-Fickian type. The developed floating microspheres of Silymarin

exhibited prolonged drug release in simulated gastric fluid for at least 12 h, and,

therefore, could potentially improve the bioavailability of the drug as well as patient

compliance.

Madan Mohan Kamila et al.,85

prepared a multiunit floating drug delivery system of

rosiglitazone maleate has been developed by encapsulating the drug into Eudragit®

RS100 through non-aqueous emulsification/solvent evaporation method. The in vitro

performances of microspheres were evaluated by yield (%), particle size analysis ,

drug entrapment efficiency, in vitro floating behaviour, surface topography, drug–

polymer compatibility, crystallinity of the drug in the microspheres, and drug release

studies. In vitro release was optimized by a {3, 3} simplex lattice mixture design to

achieve predetermined target release. The in vivo performance of the optimized

formulation was evaluated in streptozotocin-induced diabetic rats. The results showed

that floating microspheres could be successfully prepared with good yields (69–75%),

high entrapment (78-97%), narrow size distribution, and desired target release with

the help of statistical design of experiments from very small number of formulations.

In vivo evaluation in albino rats suggested that floating microspheres of rosiglitazone

could be a promising approach for better glycemic control.



3.1 DRUG PROFILE 39, 46, 62, 68, 69, 70, 71

SILYMARIN (SLM)

Chemical structure

SILYBIN

SILYDIANIN



SILYCHRISTIN

TAXIFOLIN

Molecular formula : C25H22O10

Molecular weight : 482.44 gm

Chemical name : 3, 5, 7-trihydroxy-2-[3-(4-hydroxy-3-methoxy phenyl)-2-

(hydroxy-methyl)-1,4-benzodioxan-6yl]-4-chromanone

Solubility : soluble in methanol and a buffered aqueous solution

with a pH of 2.3; solubility decreases with increasing pH in

the physiologic range.

Category : Hepato-protective agent



Description : A yellow colour powder.

pKa

: 6.8 and 6.1

Pharmacology

Silymarin (SLM), an antihepatotoxic phytocomplex, is a mixture of flavonolignans

which has been widely used as a therapeutic agent for a variety of acute and chronic

liver diseases. SLM has a potent hepato-protective effect by various mechanisms

facilitating physiology and metabolism.

Mode of action

The SLM act on the hepatic cells by following mechanisms

1. Free radical scavenging (antioxidant) action is via the glutathione system and

superoxide dismutase.

2. SLM stimulates synthesis of polymerase l, enhances ribosomal protein

synthesis and exerts a membrane stabilizing effect.

3. SLM also reduces prostaglandin Synthesis.

4. SLM is known for its hepatoprotective action against hepatic glutathione

depletion induced by ethyl alcohol and paracetamol in animal studies.

5. SLM reduces the turnover of membrane phospholipids and stabilises both

extra and intracellular membranes inside hepatocytes.

6. SLM also increases the phagocytic activity of the Kupffer cells, contributing

to hepatoprotective and regenerative effects.

Pharmacokinetics62

Absorption: The absorption by oral route is as low as 2-3 per cent of the

silybin recovered from rat bile in 24 h. About 20-40 per cent of the

administered dose.



Distribution: Vd is about 17.6 L. Protein binding is 99.8%, primarily to albumin.

Metabolism: Extensively metabolized by isoenzyme CYP2C8, with CYP2C9 as

minor pathway.

Elimination: SLM is excreted in bile as sulphates and glucuronide conjugates in

human beings5. The peak plasma levels after an oral dose are achieved in 4-6

h in experimental animals and in human beings, and elimination half-life is

approximately 6 h.

Indications and usage: Improved hepato protective activity shown in hepatitis

control of as an adjunct to diet and exercise.

Dosage and administration: Individualize therapy.

Contraindications: Established New York Heart Association class III or IV heart

failure; hypersensitivity to any component of the product.

Combination therapy

SLM has protected liver in a case of promyelocytic leukaemia receiving 6-

mercaptopurine and methotrexate. The liver toxicity was successfully treated by

800 mg of SLM and conjunction therapy was without any adverse effects70. The

drug may be of help in cisplatin induced nephrotoxicity, doxorubicin induced

apoptotic death76 and better compliance with HIV medications.

While SLM appears to have few side effects, it is not known whether it exerts any

drug interaction with interferon, ribavirin, lamivudine, or other conventional

treatment for hepatitis B or C treatment.

Over dose: SLM has been administered oral doses of up to 70-140 mg and was

well-tolerated.



Interaction 70,71,72,73,74,75,76,77

In vitro studies showed that SLM in higher concentrations has an inhibitory

effect on both phase I and phase II drug metabolizing enzymes68. The CYP3A4,

CYP2D6 and CYP2C9 are the major enzymes inhibited by this flavonolignans.

But the concentrations that obtained in plasma at pharmacological doses are

comparatively very less (about 0.5 μ moles) compared to that needed for the

inhibition of cytochrome enzymes (about 10 μ moles). Recent reports suggest

that silymarins is a potent inhibitor of hepatic UDP glucuronosyltransferase1A1

(UGT1A1), but its clinical significance is not known. However, clinicians should

take appropriate precautions while prescribing co- administered drugs which are

metabolized by similar mechanisms. Enhanced

Glucoronidation is an important phase II liver detoxification pathway.

Glucuronic acid is conjugated with toxins to facilitate their elimination from the

body via bile. SLM may similarly facilitate the bilirubin conjugation with

glucuronic acid or inhibit glucuronidase enzyme from the toxic pathogenic

intestinal bacteria. This may be of help in patients with jaundice1. SLM and

related flavonolignans displayed inhibition of catalytic activities of cytochrome

P450 isoenzymes in vitro in concentrations greatly exceeding physiologically

reachable ones and due to low solubility of silybin, it is virtually impossible to

reach such toxic concentrations in vivo. So these findings imply that no adverse

effects of SLM in terms of drug interactions should be expected.

Adverse reactions 67,68,69

SLM is reported to have a very good safety profile5. Both animal and human

studies showed that SLM is non toxic even when given at high doses (>1500

mg/day). However, a laxative effect is noted at these doses may be due to



increased bile secretion and bile flow 65. Most commonly noted adverse effects

were related to gastrointestinal tract like bloating, dyspepsia, nausea, irregular

stool and diarrhoea. It was observed in 2 to 10 per cent of patients in clinical trials,

which were similar to placebo. It also produced purities, headache, exanthema,

malaise, asthenia, and vertigo. Some serious adverse events were reported in three

patients. A 57 yr old lady developed serious symptoms of gastroenteritis

associated with collapse while the other two reported cases were allergic in nature

after ingestion of herbal tea containing SLM.

3.2 POLYMER PROFILES81

3.2.1 HYDROXY PROPYL METHYL CELLULOSE E50LV

Structural formula:

Where R is H, CH3, or CH3CH (OH) CH2

Nonproprietary names

BP : Hypromellose

JP : Hydroxypropylmethylcellulose

PhEu : Hypromellosum

USP : Hypromellose



Synonyms: Benecel MHPC; E464; hydroxy propyl methylcellulose; HPMC;

methylcellulose propylene glycol ether; methyl hydroxypropylcellulose; Metolose:

Tylopor.

Chemical name: Cellulose hydroxy propyl methyl ether.

Functional category: Coating agent; film-former; rate-controlling polymer for

sustained release; stabilizing agent; suspending agent; tablet binder; viscosity-

increasing agent.

Description: Hypromellose is an odorless and tasteless, white or creamy-white

fibrous or granular powder.

Typical properties

Acidity/alkalinity : pH = 5.5–8.0 for a 1% w/w aqueous solution.

Density (bulk) : 0.341 g/cm3.

Density (tapped) : 0.557 g/cm3.

Density (true) : 1.326 g/cm3.

Melting point : Browns at 190–200°C; chars at 225–230°C. Glass

transition

temperature is 170–180°C.

Solubility : Soluble in cold water, forming a viscous colloidal solution;

practically insoluble in chloroform, ethanol (95%) and

ether, but soluble in mixtures of ethanol and

dichloromethane, mixtures of methanol and

dichloromethane, and mixtures of water and alcohol.



Applications in pharmaceutical formulation or technology

Hypromellose is widely used in oral, ophthalmic and topical pharmaceutical

formulations. In oral products, hypromellose is primarily used as a tablet binder, in

film-coating, and as a matrix for use in extended-release tablet formulations.

Concentration between 2% and 5% w/w may be used as a binder in either wet or dry

granulation processes. High-viscosity grades may be used to retard the release of

drugs from a matrix at levels of 10–80% w/w in tablets and capsules. Depending upon

the viscosity grade; concentration of 2–20% w/w are used for film-forming solutions

to film-coat tablets. Lower-viscosity grades are used in aqueous film-coating solutions

while higher-viscosity grades are used with organic solvents.

Viscosity (dynamic)

A wide range of viscosity types are commercially available (table 3.1).

Aqueous solutions are most commonly prepared; Dichloromethane and ethanol

mixtures may also be used to prepare viscous hypromellose solutions. Solutions

prepared using organic solvents tend to be more viscous; increasing concentration

also produces more viscous solutions.



Table 3.1 Typical viscosity values for 2% (w/v) aqueous solutions of methocel,

viscosities measured at 20°C.

Methocel product USP 28 designation Nominal viscosity

(mPa s)

Methocel K100 premium LVEP 2208 100

Methocel K4M premium 2208 4000

Methocel K15M premium 2208 15 000

Methocel K100M premium 2208 100 000

Methocel E4M premium 2910 4000

Methocel F50 premium 2906 50

Methocel E10M premium CR 2906 10 000

Methocel E3 premium LV 2906 3

Methocel E5 premium LV 2906 5

To prepare an aqueous solution, it is recommended that hypromellose is

dispersed and thoroughly hydrated in about 20–30% of the required amount of water.

The water should be vigorously stirred and heated to 80–90°C and then the remaining

hypromellose should be added. Then sufficient cold water should be added to produce

the required volume.

Incompatibilities: Hypromellose is incompatible with some oxidizing agents.

Since it is nonionic, hypromellose will not complex with metallic salts or ionic

organics to form insoluble precipitates.



3.2.2 ETHYL CELLULOSE

Structural Formula :

Where ‘n’ can vary to provide a wide variety of molecular weights.

Nonproprietary Names:

BP : Ethyl cellulose.

Ph Eur : Ethyl cellulose.

USP : Ethyl cellulose.

Synonyms : Aqua coat, Ashacel, Ethocel.

Chemical Name : Cellulose ethyl ether.

Empirical Formula : C12H23O6(C12H22O5)nC12H23O5

Molecular Weight : Depend on number of n.

Functional Category : Coating agent, flavouring agent, tablet binder, tablet filler,

viscosity increasing agent.

Pharmacopoeia : IP, BP, USP.

Description : It is a tasteless, free-flowing and white to light tan

coloured powder.

pH : 5.0 to 7.5.



Density : 0.4g/cm3

.

Specific gravity : 1.12 – 1.15 g/cm3

.

Aqueous viscosity : Ethocel Std 4 premium N-7: 3.0 to 5.5. Ethocel Std 20P

premium N-7: 18.0 to 24.0. Ethocel Std 45P premium N-

7: 41.0 to 49.0.

Typical properties : Loss on drying : ≤ 3.0%.

Heavy metals : ≤ 20ppm.

Chlorides : ≤ 0.1%.

Solubility: It is practically insoluble in glycerine, propylene glycol and water. EC

that contains less than 46.5% of ethoxyl groups is freely soluble in chloroform,

methyl acetate and in mixture of aromatic hydrocarbons with ethanol (95%). EC

that contains not less than 46.5% of ethoxyl groups is freely soluble in chloroform,

ethanol, methanol and toluene.

Stability: It is stable, slightly hygroscopic material, resistant to alkalis both dilute

and concentrated and to salt solutions.

Storage Conditions: It should be stored at a temperature of 32°C, away from all

sources of heat.

Incompatibilities: It is incompatible with paraffin wax and microcrystalline wax.

Safety: It is not metabolized following oral consumption and is therefore a

noncalorific substance. Because it is not metabolized, therefore it is not

recommended for parenteral products. It is generally regarded as a nontoxic,

nonallergenic and nonirritating material.

Applications: It is used in oral and topical pharmaceutical formulations mainly as

a hydrophobic coating agent for tablets and granules. Ethyl cellulose coating are

used to modify the release of a drug, to mask an unpleasant taste or to improve the



stability of a formulation, where as granules are coated to inhibit oxidation. When

dissolved in an organic solvent or mixture can be used on its own to produce water

insoluble films. Higher viscosity grades tend to produced stronger and more

durable films. Also used as a thickening agent in creams, lotions or gels provided

an appropriate solvent is used.

.

CHAPTER 4 MATERIALS AND METHODS

Department of Pharmaceutics, Sarada Vilas College of Pharmacy Page 47

4.1 MATERIALS

The following materials of Pharma grade or the best possible Laboratory

Reagent (LR) were used as supplied by the manufacturer. The double distilled water

was used in all experiments.

Table 4.1: List of chemicals used with grade and supplier

Sl.

no. Materials used Grade Manufacturer

1. Silymarin(SLM) Pharma

grade

Aeon formulations Pvt. Ltd.

Chennai , India

2. Hydroxy propyl methyl

cellulose K 15 M LR Shreeji chemicals, Mumbai

3. Ethyl cellulose LR Rolex chemicals, Mumbai

4. Methanol LR Shreeji chemicals, Mumbai

5. Ethanol LR S D fine chemical Ltd, Mumbai

6. Tween 80 LR S D fine chemical Ltd, Mumbai

7. Dichloromethane LR S D fine chemical Ltd, Mumbai

8. Potassium dihydrogen

phosphate LR S D fine chemical Ltd, Mumbai

9. Potassium chloride LR Qualigens fine chemicals Mumbai

10. Hydrochloric acid LR Central drug house (p) Ltd, Bombay

11. Sodium hydroxide pellets LR S D Fine chemical Ltd, Mumbai

4. MATERIALS AND METHODS



Table 4.2: List of instruments used

Sl.

No. Instrument Manufacturer

1. UV visible spectrophotometer Shimadzu Corporation, Japan.

2. FTIR spectrophotometer IR-Affinity-1, Shimadzu, Japan.

3. Magnetic stirrer Remi motors, Ahmedabad.

4. Mechanical stirrer Remi motors, Ahmedabad

5. Centrifuge Remi motors, Ahmedabad.

6. SEM, JSM – 8400A JEOL, Japan.

7. Electronic balance Citizen scales Pvt. Ltd.

8. Digital pH meter

Digisun Electronics, Hyderabad.

9. DSC Mettler-Toledo star 822e

system,

Switzerland

10. Digital melting point apparatus CL 725/726, Microcontroller based melting

point apparatus

11. XRD Joel JDX-8030, Japan

12. USP dissolution XXIII

apparatus Electrolab TDL-08L

13. Hot air oven Techno scientific, Bangalore

14. Microscope Mvtex SM-3JR



4.2 METHODS

4.2.1 Preformulation studies

Preformulation testing is the first step in the rationale development of dosage

forms of a drug substance. It can be defined as an investigation of physical and

chemical properties of a drug substance alone and when combined with excipients.

The overall objective of preformulation testing is to generate information useful to the

formulator in developing stable and bioavailable dosage forms, which can be mass-

produced.

Solubility

Solubility of SLM was determined in methanol, acetone, 0.1M HCL.

Melting point determination

Melting point of SLM was determined by open capillary method.

Determination of λmax

A solution of SLM containing the concentration 10 µg/ ml was prepared in

methanol and UV spectrum was taken using Shimadzu (UV-2450) double beam

spectrophotometer. The solution was scanned in the range of 200 – 600nm.



4.3 FORMULATION DESIGN

Table 4.3 Formulation design for SLM floating microspheres using different ratios of

drug and polymers.

Sl.no Batch code SLM : HPMCE 50 LV:EC

1. SLM-1 0.3 : 0.7 : 1.0

2. SLM-2 0.3 : 0.7 : 1.5

3. SLM-3 0.3 : 0.7 : 2.0

4. SLM-4 0.3 : 0.7 : 2.5

5. SLM-5 0.3 : 0.7 : 3.0

6. SLM-6 0.3 : 0.7 : 3.5

Preparation of SLM floating microspheres 40

Method used: Emulsification – solvent evaporation method

Floating microspheres were prepared by solvent evaporation technique

accurately weighed drug HPMC E50 LV and EC were dissolved in ethanol and

dichloromethane (1:1) to form a homogenous polymer solution. This solution is

poured in 250 ml water containing 0.01% tween 80 maintained at 30-400C

subsequently stirred at ranging agitation speed for 30 min to allow the volatile liquid

to evaporate. The microspheres formed were filtered, washed with water and dried in

vacuum. The microspheres were then stored in a desiccator over fused calcium

chloride.

4.4 EVALUATION OF SLM FLOATING MICROSPHERES

4.4.1 Drug polymer interaction (FTIR) study 41, 42

FTIR spectroscopy was performed on Fourier transformed infrared

spectrophotometer (IR-Affinity-1, Shimadzu, Japan). The pellets of drug and

potassium bromide were prepared by compressing the powders at 20 psi for 10 min on



KBr-press and the spectra were scanned in the wave number range of 4000- 600 cm-1

.

FTIR study was carried on SLM, physical mixture of SLM and polymers, SLM

loaded microspheres and blank microspheres.

4.4.2 Surface morphology (SEM) 41, 42

Scanning electron microscopy has been used to determine particle size

distribution, surface topography, texture, and to examine the morphology of fractured

or sectioned surface. SEM is probably the most commonly used method for

characterizing drug delivery systems, owing in large to simplicity of sample

preparation and ease of operation. SEM studies were carried out by using JEOL JSM

T-330A scanning microscope (Japan). Dry SLM floating microspheres were placed

on an electron microscope brass stub and coated with in an ion sputter. Picture of

SLM floating microspheres were taken by random scanning of the stub.

4.4.3 Frequency distribution analysis

Determination of average particle size of SLM floating microspheres was

carried out by optical microscopy in which stage micrometer was employed. A minute

quantity of SLM floating microspheres was spread on a clean glass slide and average

size of 300 SLM floating microspheres was determined in each batch. In order to be

able to define a frequency distribution or compare the characteristics of particles with

many different diameters, the frequency distribution can be broken down into

different size ranges, which can be presented in the form of a histogram. Histogram

presents an interpretation of the frequency distribution and enables the percentage of

particles having a given equivalent diameter to be determined.

4.4.4 Percentage yield

Percentage practical yield of SLM floating microspheres is calculated to know

about percentage yield or efficiency of any method, thus it helps in selection of



appropriate method of production. Practical yield was calculated as the weight of

SLM floating microspheres recovered from each batch in relation to the sum of

starting material.

The percentage yield of prepared SLM floating microspheres was determined

by using the formula.

4.4.5 Buoyancy percentage

Fifty milligrams of the floating microspheres were placed in 0.1M HCL, 100 ml

containing 0.02 w/v% Tween 80. The mixture was stirred at 100 rpm in a magnetic

stirrer. After 12 hrs, the layer of buoyant microspheres was pipette and separated by

filtration. Particles in the sinking particulate layer were separated by filtration.

Particles of both types were dried in a desiccator until constant weight. Both the

fractions of microspheres were weighed and buoyancy was determined by the weight

ratio of floating particles to the sum of floating and sinking particles.

Where;

Wf and Ws are the weights of the floating and settled microspheres, respectively.

4.4.6 Determination of percentage drug entrapment (PDE) 43, 44

Efficiency of drug entrapment for each batch was calculated in terms of

percentage drug entrapment as per the following formula.



Preparation of standard calibration curve of SLM in methanol

Scanning of silymarin by UV-spectrophotometer in methanol

I Stock: 100 mg of SLM was accurately weighted into 100 ml volumetric flask,

dissolved in methanol and volume was made up with methanol. II Stock: Pipette 1ml

of above solution into another 10 ml volumetric flask and the volume was made with

methanol.

Procedure for calibration of SLM in methanol at λmax 287nm

From the SLM standard stock solution (1000µg/ml), 1ml solution was diluted

to 10 ml using methanol solution to get concentrations of 100 µg/ml. from this

solution, aliquots of 0.2 ml, 0.4 ml,0.6 ml,0.8 ml,0.10 ml from standard drug solution

were diluted to 10 ml with methanol. The absorbance of these solutions was measured

at 287 nm methanol as a blank.

Theoretical drug content

Theoretical drug content was determined by calculation assuming that the entire

SLM present in the polymer solution used gets entrapped in SLM floating

microspheres, and no loss occurs at any stage of preparation of SLM floating

microspheres.

Practical drug content

Procedure: Practical drug content was analyzed by using the following procedure,

weighed amount of SLM floating microspheres equivalent to 10 mg of SLM floating

microspheres was dissolved in 100 ml of 0.1M HCL. This solution was kept overnight

for the complete dissolution of the SLM floating microsphere in 0.1M HCL. This

solution was filtered and further diluted to make a conc of 10 µg/ml solution. The

absorbance of the solutions was measured at 287 nm using double beam UV-Visible



spectrophotometer against 0.1M HCL solution as blank and calculated for the

percentage of drug present in the sample.

4.4.7 In vitro dissolution studies

Calibration curve of SLM in methanol.

The procedure for the calibration of Silymarin is same as mentioned under

determination of percentage drug entrapment.

Procedure for Invitro dissolution study

The release rate of SLM floating microspheres was determined by employing

USP XXIII apparatus by rotating paddle method. The dissolution test was performed

using 900 ml 0.1M HCL, in 37 ± 0.5°C at 50 rpm. SLM floating microspheres

equivalent to 100 mg were placed in a basket to avoid floating of microspheres. A

sample (5 ml) of the solution was withdrawn from the dissolution apparatus hourly for

12 hrs, and the samples were replaced with fresh dissolution medium. The samples

were passed through whatman filter paper and the absorbance of these solutions was

measured at 287 nm. Dissolution profiles of the formulations were analyzed by

plotting drug release versus time plot. Data obtained was also subjected to kinetic

treatment to understand release mechanism.

4.4.8 Kinetics of drug release

To examine the drug release kinetics and mechanism, the cumulative release data

were fitted to models representing zero order (Q v/s t), first order [Log(Q0-Q) v/s t],

Higuchi’s square root of time (Q v/s t1/2

) and Korsemeyer Peppas double log plot (log Q

v/s log t) respectively, where Q is the cumulative percentage of drug released at time t and

(Q0-Q) is the cumulative percentage of drug remaining after time t.

In short, the results obtained from in vitro release studies were plotted in four

kinetics models of data treatment as follows.



Cumulative percentage drug release Vs. Time (zero order rate kinetics)

Log cumulative percentage drug retained Vs. Time (first order rate kinetics)

Cumulative percentage drug release Vs. √T (Higuchi’s classical diffusion equation)

Log of cumulative percentage drug release Vs. log Time(Peppas exponential

equation)

4.4.9 Differential Scanning Calorimetery (DSC) 45

The physical state of drug in the SLM floating microspheres was analyzed by

DSC (Mettler-Toledo star 822e

system, Switzerland). The thermo grams of SLM,

physical mixture of SLM and polymer, SLM floating microspheres and Blank

microsphere were obtained at a scanning rate of 10°C/min conducted over a

temperature range of 25–350ºC, respectively.

CHAPTER 5 RESULTS

Department of Pharmaceutics, Sarada Vilas college of Pharmacy Page 56

5.1 PREFORMULATION STUDIES

Solubility study

SLM was found to be freely soluble in methanol, 0.1M

HCL, sparingly soluble in water and acetone.

Melting point determination

The melting point of SLM was found to be 125-128o

C.

Determination of λmax

Fig 5.1 UV spectra of SLM at 10 µg/ml concentration

Table 5.1 Wavelength of maximum absorption of SLM in methanol

Sl. No. Solvent λmax

1 Methanol 287

5. RESULTS

CHAPTER 5 RESULTS



5.2.1 Drug polymer interaction (FTIR) study

From the spectra of SLM, physical mixture of SLM and polymer, SLM microspheres

and blank microspheres, it was observed that all characteristic peaks of SLM were

present in the combination spectrum, thus indicating compatibility of the SLM and

polymer. IR Spectra shown in Fig 5.2 to 5.5 data shown in table 5.2.

410.

2

540.

0

736.

0

792.

0

829.

0

1284

.0

1625

.6

3410

.73740

.0

S IL

-10

-5

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

%T

rans

mitt

ance

500 1000 1500 2000 2500 3000 3500 4000

W avenumbers (cm-1)

Fig 5.2 IR spectra of SLM

CHAPTER 5 RESULTS


577

.4

828

.0

888

.0

956

.0

112

2.9

127

6.0

138

4.0

145

2.0

152

4.0

162

6.3

205

9.2

284

0.0

288

1.5

294

4.0

297

5.7

346

3.7

367

2.5

373

6.8

MIX D&S

-10

-5

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

%T

ransm

itta

nce

500 1000 1500 2000 2500 3000 3500 4000

W avenumbers (cm-1)

Fig 5.3 IR spectra of physical mixture SLM ,HPMC K15 M and EC

466

.5

666

.4

882

.5

928

.0

105

5.7

127

7.3

137

6.4

144

8.4

163

7.6

173

8.6

287

4.6

293

0.2

297

4.9

345

5.1

374

7.2

MS

46

48

50

52

54

56

58

60

62

64

66

68

70

72

74

76

78

80

82

84

86

88

90

92

94

96

98

100

%T

ransm

itta

nce

500 1000 1500 2000 2500 3000 3500 4000

W avenumbers (cm-1)

Fig 5.4 IR specra of floating microspheres using mixture of

HPMC E50 LV and EC and SLM

CHAPTER 5 RESULTS


472

568

.7

616

.0

668

.0

856

.0

944

.3

105

3.4

113

2.0

131

6.2

137

8.6

145

4.6

162

6.6

166

0.8

206

0.5

283

2.6

288

3.1

294

4.1

298

0.2

347

1.5

373

6.6

HP MC

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

%T

ransm

itta

nce

500 1000 1500 2000 2500 3000 3500 4000

W avenumbers (cm-1)

Fig 5.5 IR spectra of HPMC E 50 LV and EC floating microspheres

CHAPTER 5 RESULTS


5.2.2 Surface morphology of SLM microspheres (SEM)

SLM3, refers to SLM floating microspheres prepared by using HPMC E 50 LV and

EC with drug: polymer ratio 0.3 : 0.7: 2

Fig 5.6 SEM photographs of SLM floating microspheres

CHAPTER 5 RESULTS



Determination of Average particle size

Table 5.2 Average diameter of SLM floating microspheres.

Sl. No Formulation code Average size (µm)±SEM

1 SLM1 187.5±1.10

2 SLM2 337±1.00

3 SLM3 287.34±1.04

4 SLM4 387.6±0.91

5 SLM5 537±1.10

6 SLM6 496.69±1.78

SD Standard deviation (n=3)

Fig 5.7 Average diameter of SLM floating microspheres

CHAPTER 5 RESULTS


Frequency distribution analysis

Table 5.3 Frequency distribution data of SLM floating microspheres.

Size range

(µm)

Number of particles

SLM1

SLM2 SLM3 SLM4 SLM5 SLM6

0-100 56 37 18 20 33 28

100-200 84 36 42 38 42 40

200-300 72 92 33 46 17 25

300-400 35 74 84 72 58 58

400-500 37 28 58 97 87 85

500-600 16 43

65 37 63 64

0-1

00

100-2

00

200-3

00

300-4

00

400-5

00

500-6

00

0-1

00

100-2

00

200-3

00

300-4

00

400-5

00

500-6

00

0-1

00

100-2

00

200-3

00

300-4

00

400-5

00

500-6

00

0-1

00

100-2

00

200-3

00

300-4

00

400-5

00

500-6

00

0-1

00

100-2

00

200-3

00

300-4

00

400-5

00

500-6

00

0-1

00

100-2

00

200-3

00

300-4

00

400-5

00

500-6

00

0

5 0

1 0 0

1 5 0S L M 1

S L M 2

S L M 3

S L M 4

S L M 5

S L M 6

S iz e r a n g e (µ m )

Fr

eq

ue

nc

y d

istr

ibu

tio

n

Fig 5.8 Frequency distribution of SLM floating microspheres

CHAPTER 5 RESULTS



Table 5.4 Buoyancy percentage of SLM floating microspheres

Sl.no Formulation code % Buoyancy time

1 SLM1 100

2 SLM2 100

3 SLM3 100

4 SLM4 100

5 SLM5 100

6 SLM6 100


5.2.5 Percentage drug entrapment efficiency

Calibration curve of SLM at λmax 287nm

Table 5.5 Calibration data of SLM in methanol

Sl. No Concentration (µg/ml) Absorbance

1 6 0.247

2 8 0.326

3 10 0.398

4 12 0.483

5 14 0.559

6 16 0.634

CHAPTER 5 RESULTS


Fig 5.9 Calibration curve of Silymarin in methanol

Table 5.6 Drug entrapment efficiency of SLM floating microspheres

Sl.no

Formulation

Code

Percentage

yield Drug loading (%)

Entrapment

efficiency (%)

1 SLM1 83.90 87 58.78±1.02

2 SLM2 92.00 83 69.1±1.11

3 SLM3 73.33 86 87.2±2.25

4 SLM4 80.55 79 93.46±1.10

5 SLM5 73.00 68 91.32±0.98

6 SLM6 84.44 62 93.53±1.12


CHAPTER 5 RESULTS


F O R M U L A T IO N C O D E

% E

NT

RA

PM

EN

T E

FF

ICIE

NC

Y

SL

M1

SL

M2

SL

M3

SL

M4

SL

M5

SL

M6

0

2 0

4 0

6 0

8 0

1 0 0

Fig 5.10 Drug entrapment efficiency of SLM floating microspheres

CHAPTER 5 RESULTS



Table 5.7 In vitro release data of SLM floating microspheres

Sl.no. Time (h) % Cum. drug release

SLM1 ± SD SLM2 ± SD SLM3 ± SD

1 0 0 0 0

2 1 38.51 ± 0.25 34.19 ± 0.49 26.08 ± 0.15

3 2 49.07 ± 0 44.55 ± 0.00 33.95 ± 0.36

4 3 56.82 ± 0.17 50.41 ± 0.01 38.89 ± 0.90

5 4 67.22 ± 0.013 55.68 ± 0.70 43.57 ± 0.04

6 5 76.44 ± 0.07 63.00 ± 0.00 50.57 ± 0.26

7 6 85.50 ± 0.0 70.45 ± 0.94 54.70 ± 0.77

8 7 90.90 ± 00 73.37 ± 0.23 59.49 ± 0.92

9 8 98.90 ± 0.16 82.60 ± 3.0 61.61 ± 0.07

10 9 - 89.25 ± 0.00 68.92 ± 0.23

11 10 - 98.10 ± 0.60 74.54± 0.00

12 11 - 98.58 ± 1.0 78.38 ± 0.12

13 12 - - 82.16 ± 0.90

% Cum. drug release


0 0 0

25.75 ± 0.00 12.16 ± 0.14 9.08 ± 0.144

33.75 ± 0.42 18.0 ± 0.00 11.36 ± 0.06

38.28 ± 0.00 24.26 ± 0.80 17.24 ± 0.44

43.38 ± 0.24 31.42 ± 0.11 23.46 ± 0.05

49.07 ± 0.10 34.29 ± 0.00 29.53 ± 0.40

53.28 ± 0.24 39.51 ± 0.03 31.88 ± 0.21

57.38± 0.00 44.36 ± 0.40 35.37 ± 0.31

63.28 ± 0.25 45.54 ± 0.31 41.33 ± 0.39

68.43± 0.23 50.88 ± 0.30 43.42 ± 0.14

73.60± 0.00 53.79 ± 0.25 46.88 ± 0.37

76.20 ± 0.06 55.29 ± 0.25 48.20 ± 0.35

79.45 ± 0.09 58.55 ± 0.19 51.51 ± 0.06

SD=Standard deviation (n=3). The differences in mean of % cumulative drug release

between batch series SLM1-SLM6 were significant (p < 0.0001).

CHAPTER 5 RESULTS


TIM E (h rs )

%C

um

. d

ru

g r

ele

as

e

0 5 1 0 1 5

0

5 0

1 0 0

1 5 0

S L M 1

S L M 2

S L M 3

S L M 4

S L M 5

S L M 6

Fig 5.11 Comparative in vitro release profile of SLM floating microspheres

CHAPTER 5 RESULTS


5.2.7 Release kinetics of SLM floating microspheres

Table 5.8 Zero order release kinetics data of SLM floating microspheres

Sl.no. Time (h) % Cum. drug release


1 0 0 0 0

2 1 38.51 ± 0.25 34.19 ± 0.49 26.08 ± 0.15

3 2 49.07 ± 0 44.55 ± 0.00 33.95 ± 0.36

4 3 56.82 ± 0.17 50.41 ± 0.01 38.89 ± 0.90

5 4 67.22 ± 0.013 55.68 ± 0.70 43.57 ± 0.04

6 5 76.44 ± 0.07 63.00 ± 0.00 50.57 ± 0.26

7 6 85.50 ± 0.0 70.45 ± 0.94 54.70 ± 0.77

8 7 90.90 ± 00 73.37 ± 0.23 59.49 ± 0.92

9 8 98.90 ± 0.16 82.60 ± 3.0 61.61 ± 0.07

10 9 - 89.25 ± 0.00 68.92 ± 0.23

11 10 - 98.10 ± 0.60 74.54± 0.00

12 11 - 98.58 ± 1.0 78.38 ± 0.12

13 12 - - 82.16 ± 0.90

% Cum. drug release


0 0 0

25.75 ± 0.00 12.16 ± 0.14 9.08 ± 0.144

33.75 ± 0.42 18.0 ± 0.00 11.36 ± 0.06

38.28 ± 0.00 24.26 ± 0.80 17.24 ± 0.44

43.38 ± 0.24 31.42 ± 0.11 23.46 ± 0.05

49.07 ± 0.10 34.29 ± 0.00 29.53 ± 0.40

53.28 ± 0.24 39.51 ± 0.03 31.88 ± 0.21

57.38± 0.00 44.36 ± 0.40 35.37 ± 0.31

63.28 ± 0.25 45.54 ± 0.31 41.33 ± 0.39

68.43± 0.23 50.88 ± 0.30 43.42 ± 0.14

73.60± 0.00 53.79 ± 0.25 46.88 ± 0.37

76.20 ± 0.06 55.29 ± 0.25 48.20 ± 0.35

79.45 ± 0.09 58.55 ± 0.19 51.51 ± 0.06



CHAPTER 5 RESULTS


Table 5.9 First order release kinetics data of SLM floating microspheres.

Sl.no. Time (h) Log % Drug remaining to be released


1 0 2.00±0.00 2.00±0.00 2 ± 0.000

2 1 1.790 ± 0.00 1.820±00 1.868±0.10

3 2 1.754 ± 0.00 1.740±0.00 1.820±0.23

4 3 1.635 ± 0.100 1.696±0.00 1.752±0.23

5 4 1.514 ± 0.002 1.644±0.10 1.715±0.10

6 5 1.371 ± 0.100 1.568±0.00 1.695±0.20

7 6 1.161 ± 0.000 1.473±0.04 1.620±0.23

8 7 0.952 ± 0.048 1.360±0.04 1.608±0.10

9 8 0.061 ± 0.000 1.267±0.00 1.160±0.20

10 9 - 1.249±0.00 1.591±0.32

11 10 - 0.267±1.00 1.406±0.00

12 11 - 0.146±0.00 1.356±0.52

13 12 - 1.253±0.03

Log% Drug remaining to be release


2 ± 0.000 2 ± 0.000 2 ± 0.000

1.871±0.00 1.943±0.10 1.959±0.01

1.820±0.10 1.914±0.00 1.947±0.00

1.790±0.10 1.874±0.20 1.918±0.00

1.753±0.10 1.837±0.00 1.882±0.00

1.707±0.00 1.818±0.00 1.848±0.02

1.670±0.03 1.800±0.20 1.822±0.02

1.630±0.03 1.796±0.00 1.802±0.10

1.560±0.00 1.736±0.00 1.768±0.02

1.492±0.00 1.691±0.00 1.752±0.00

1.422±0.00 1.664±0.02 1.725±0.02

1.370±0.00 1.653±0.02 1.714±0.02

1.313±0.00 1.616±0.00 1.684±0.23


between batch series SLM1-SLM6 were significant (p < 0.0001)

CHAPTER 5 RESULTS


Table 5.10 Higuchi matrix release kinetics data of SLM floating microspheres

Sl.no. √T (h) % Cum. drug release


1 0 0 0 0

2 1.000 38.51 ± 0.25 34.19 ± 0.49 26.08 ± 0.15

3 1.414 49.07 ± 0 44.55 ± 0.00 33.95 ± 0.36

4 1.732 56.82 ± 0.17 50.41 ± 0.01 38.89 ± 0.90

5 2.000 67.22 ± 0.013 55.68 ± 0.70 43.57 ± 0.04

6 2.236 76.44 ± 0.07 63.00 ± 0.00 50.57 ± 0.26

7 2.449 85.50 ± 0.0 70.45 ± 0.94 54.70 ± 0.77

8 2.645 90.90 ± 00 73.37 ± 0.23 59.49 ± 0.92

9 2.828 98.90 ± 0.16 82.60 ± 3.0 61.61 ± 0.07

10 3.000 - 89.25 ± 0.00 68.92 ± 0.23

11 3.162 - 98.10 ± 0.60 74.54± 0.00

12 3.316 - 98.58 ± 1.0 78.38 ± 0.12

13 3.464 - - 82.16 ± 0.90

% Cum. drug release


0 0 0

25.75 ± 0.00 12.16 ± 0.14 9.08 ± 0.144

33.75 ± 0.42 18.0 ± 0.00 11.36 ± 0.06

38.28 ± 0.00 24.26 ± 0.80 17.24 ± 0.44

43.38 ± 0.24 31.42 ± 0.11 23.46 ± 0.05

49.07 ± 0.10 34.29 ± 0.00 29.53 ± 0.40

53.28 ± 0.24 39.51 ± 0.03 31.88 ± 0.21

57.38± 0.00 44.36 ± 0.40 35.37 ± 0.31

63.28 ± 0.25 45.54 ± 0.31 41.33 ± 0.39

68.43± 0.23 50.88 ± 0.30 43.42 ± 0.14

73.60± 0.00 53.79 ± 0.25 46.88 ± 0.37

76.20 ± 0.06 55.29 ± 0.25 48.20 ± 0.35

79.45 ± 0.09 58.55 ± 0.19 51.51 ± 0.06



CHAPTER 5 RESULTS


Table 5.11 Peppas release kinetics data of SLM floating microspheres

Sl.no. Log T (h) Log % drug release


1 0 0 0 0

2 0 1.533 ± 0.00 1.528 ±0.00 1.412 ± 0.03

3 0.301 1.699 ± 0.00 1.640 ±0.00 1.532 ± 0.26

4 0.477 1.754 ± 0.00 1.715 ±0.00 1.582 ± 0.11

5 0.602 1.826 ± 0.00 1.748 ±0.00 1.637 ± 0.11

6 0.698 1.882 ± 0.00 1.799 ±0.00 1.700 ± 0.25

7 0.778 1.932 ± 0.00 1.847 ±0.01 1.737 ± 0.30

8 0.845 1.952 ± 0.05 1.888 ±0.03 1.744 ± 0.00

9 0.903 1.995 ± 0.00 1.915 ±0.00 1.790 ± 0.11

10 0.954 - 1.951 ±0.00 1.862 ±0.20

11 1.000 - 1.991 ±0.00 1.872 ±0.00

12 1.041 - 1.994 ±0.01 1.894 ±0.02

13 1.079 - - 1.914 ±0.11

Log% drug release


0 0 0

1.411 ±0.00 1.080 ±0.03 0.957 ± 0.50

1.529 ± 0.02 1.255 ±0.00 1.060 ± 0.00

1.583 ±0.00 1.385 ± 0.30 1.237 ± 0.00

1.636 ±0.00 1.495 ± 0.00 1.375 ± 0.00

1.691 ±0.01 1.535 ± 0.00 1.470 ± 0.00

1.725 ±0.02 1.560 ± 0.02 1.500 ± 0.03

1.759 ±0.00 1.646 ± 0.00 1.562 ± 0.02

1.800 ±0.02 1.659 ± 0.00 1.616 ± 0.00

1.835 ± 0.00 1.706 ± 0.00 1.638 ± 0.03

1.862 ±0.00 1.728 ± 0.02 1.671 ± 0.00

1.880 ±0.00 1.743 ± 0.01 1.683 ± 0.01

1.900 ±0.00 1.823 ± 0.00 1.711 ± 0.28



CHAPTER 5 RESULTS


T im e (h rs )

%C

um

ula

tiv

e d

ru

g r

ele

as

e

0 5 1 0 1 5

0

5 0

1 0 0

1 5 0S L M 1

S L M 2

S L M 3

S L M 4

S L M 5

S L M 6

Fig 5.12 Zero order release kinetics profile of SLM floating microspheres

T IM E (h r s)

Lo

g %

D

ru

g r

em

ain

ing

to

be

re

lea

se

d

5 1 0 1 5

-0 .5

0 .0

0 .5

1 .0

1 .5

2 .0

2 .5

S L M 1

S L M 2

S L M 3

S L M 4

S L M 5

S L M 6

Fig 5.13 First order release kinetics profile of SLM floating microspheres

CHAPTER 5 RESULTS


%C

um

ula

tiv

e d

ru

g r

ele

as

e

0 1 2 3 4

0

5 0

1 0 0

1 5 0S L M 1

S L M 2

S L M 3

S L M 4

S L M 5

S L M 6

)(hrsT

Fig 5.14 Higuchi matrix diffusion release kinetics profile of SLM floating

microspheres

L o g T (h )

Lo

g %

dr

ug

re

lea

se

0 .0 0 .5 1 .0 1 .5

0

1

2

3S L M 1

S L M 2

S L M 3

S L M 4

S L M 5

S L M 6

Fig. 5.15 Peppas model release kinetics profile of SLM floating microspheres

CHAPTER 5 RESULTS


Table 5.12 Regression co-efficient (r2) values of different kinetic models and

diffusion exponent (n) of Peppas model for SLM floating microspheres.

Formulation Zero order First order Higuchi

Matrix

Peppas plot

r2

value ‘n’ value

SLM1 0.9117 0.8256 0.9674 0.9736 0.5290

SLM2 0.9195 0.8634 0.9896 0.9800 0.5509

SLM3 0.9771 0.9352 0.9923 0.9842 0.6206

SLM4 0.9851 0.9323 0.9939 0.9856 0.9894

SLM5 0.9913 0.9575 0.9886 0.9963 0.9593

SLM6 0.9913 0.9828 0.9923 0.9842 0.9734

5.2.8 DSC Thermograms

Fig 5.16 DSC thermogram of SLM

CHAPTER 5 RESULTS


Fig 5.17 DSC thermogram of physical mixture of SLM, HPMC E 50 LV and EC

CHAPTER 5 RESULTS


Fig 5.18 DSC thermogram of SLM floating microspheres

CHAPTER 6 DISCUSSION

Department of pharmaceutics, Sarada Vilas college of pharmacy 77

Gastro retentive systems have potential to remain in the gastric region for

several hours and hence significantly prolong the gastric residence time of drugs.

Prolonged gastric retention improves bioavailability, reduces drug waste, and

improves solubility for drugs that are less soluble in a high pH environment. It has

applications also for local drug delivery to the stomach and proximal small intestines.

The aim of the study was to formulate and characterize the floating

microspheres of SLM by solvent evaporation technique with HPMC E 50 LV, EC, as

polymers, in different concentration of polymer.

In the present work, total six formulations were prepared and the detailed

composition is shown in Table.4.3 The prepared SLM floating microspheres were

then subjected to FTIR, SEM, particle size, size distribution, % yield, drug content,

entrapment efficiency, in vitro dissolution, release kinetics and DSC.

6.1 PREFORMULATION STUDIES

The solubility of SLM in 10 mg/10 ml of solvent was carried out and it

reveals that it is soluble in methanol, acetone, 0.1M HCL.

The melting point of SLM was found to be 125 -128 0

C.

A solution of SLM containing the conc 10 µg/ ml was prepared in methanol

and UV spectrum was taken using Shimadzu (UV-2450) double beam

spectrophotometer. The solution was scanned in the range of 200 – 400 nm. It

was found to be 287nm.

6. DISCUSSION




6.2.1 Drug polymer interaction (FTIR) study

FTIR Spectra were obtained for SLM, physical mixture of SLM and polymer,

SLM microspheres, blank microspheres and physical mixture of SLM and blank

microspheres were presented in Fig 5.2 to 5.5, the characteristic peaks of the SLM

were compared with the peaks obtained for physical mixture of SLM and polymer,

formulations were given in table.5.2. The characteristics peaks found in SLM,

physical mixture and formulations, hence it appears there was no chemical interaction

between SLM and polymer and it can be concluded that the characteristics bands of

SLM were not affected after successful loading.

6.2.2 Surface morphology (SEM)

The surface morphology of the SLM floating microspheres was studied by SEM

(Fig 5.6). Surface smoothness of the SLM floating microspheres was increased by

increasing the polymer concentration, which was confirmed by SEM. At lower

polymer concentration (0.3:0.7:1) rough and wrinkled surface of SLM floating

microspheres was obtained and at higher polymer concentration (0.3:0.7:4.5) the SLM

floating microspheres with smooth surface was obtained.


As the SLM to polymer ratio was increased, the mean particle size of SLM

floating microspheres was also increased (Table 5.3). The significant increase may be

because of the increase in the viscosity of the droplets (may be due to the increase in

concentration. of polymer solution). SLM floating microspheres having a size range

of 100 to 537 µm (Table 5.3) with normal frequency distribution was obtained.




The microspheres floated for prolonged time over the surface of the dissolution

medium without any apparent gelation. As the polymer concentration increases the

buoyancy time increases. Percentage buoyancy of the microspheres was in the range

100 % after 12 hrs. The results obtain are given in Table 5.4.

6.2.5 Percentage yield

The percentage yield for SLM floating microspheres were 83.9%, 92%, 73.33%,

80.85%, 73% and 84.44% for formulation SLM1,SLM2, SLM3, SLM4, SLM5,

SLM6 respectively (table 5.6).

6.2.6 Percentage drug entrapment efficiency

Entrapment efficiency increases with increase in the polymer concentration.

From the results it can be inferred that there is a proper distribution of SLM in the

microspheres and the deviation is within the acceptable limits.

The percent of drug content in the formulations was found to be in the range of

48% to 77%. The percentage entrapment efficiency was found to be 58.4% to 93.5%.

The results obtained are given in table. 5.6. and their histograms shown in Fig 5.10. A

maximum of 93.50% drug entrapment efficiency was obtained in the SLM floating

microspheres which were prepared by using HPMC E 50 LV and EC. It was further

observed that the drug entrapment was proportional to the SLM: polymer ratio and

size of the SLM floating microspheres. By increasing the polymer concentration, the

encapsulation efficiency was increased.


The in vitro performance of SLM floating microspheres showed prolonged and

controlled release of SLM. The results of the in vitro dissolution studies shows

controlled and predictable manner as the polymer concentration increases the drug



release from the floating microsphere decreases. The formulations SLM1 93.53% to

SLM6 56.47% are shown in table 5.8 and Fig 5.11.

6.2.8 Release kinetics of SLM floating microspheres

The plots of cumulative percentage drug release V/s. time, cumulative percent

drug retained V/s. root time, log cumulative percent drug retained V/s. time and log

cumulative percent drug release V/s. log time were drawn and represented graphically

as shown in Fig 5.11 to 5.15 and table 5.7 to 5.12 respectively. The slopes and the

regression co-efficient of determinations (r2) were listed in Table 5.12. The co-

efficient of determination indicated that the release data was best fitted with zero

order kinetics. Higuchi equation explains the diffusion controlled release mechanism.

The diffusion exponent ‘n’ values of Korsemeyer-Peppas model was found to be in

the range of 0.5 to 1 for the SLM floating microspheres prepared with HPMC E 50

LV and EC indicating Non-Fickian release of drug through SLM floating

microspheres.

6.2.9 Differential scanning colorimetry (DSC)

In order to confirm the physical state of SLM in the microspheres, DSC of the

SLM, physical mixture of SLM and polymers and SLM loaded floating microspheres

were carried out and shown in Fig 5.16 to 5.18. The DSC trace of SLM showed a

sharp endothermic peak at 125°C, its melting point. The physical mixture of SLM and

polymers showed the same thermal behavior 1250C as the individual component,

indicating that there was no interaction between the SLM and the polymer in the solid

state. The melting point range of SLM is between 125 -128 0C thus indicating there is

no change of SLM in pure state, physical mixture of drug and polymer. The absence



of endothermic peak of the SLM at 125 0

C the DSC of the SLM floating

microspheres suggests that the SLM existed in an amorphous or disordered crystalline

phase as a molecular dispersion in polymeric matrix.

CHAPTER 7 CONCLUSION


The concept of formulating floating microspheres containing SLM offers a

suitable, practical approach to achieve a prolonged therapeutic effect by continuously

releasing the medication over extended period of time. In present work, floating

microspheres of SLM were prepared successfully by solvent evaporation method

using the different concentration and combination of polymers like HPMC E50 LV,

and EC.

From the above experimental results it can be concluded that:

Preformulation studies like melting point, solubility and UV analysis of were

complied with standards.

The FTIR Spectra revealed that, there was no interaction between polymers and

SLM. All the polymers used were compatible with the SLM.

Surface smoothness of the SLM microspheres was increased by increasing the

polymer concentration, which was confirmed by SEM.

As the drug to polymer ratio was increased, the mean particle size of SLM

floating microspheres was also increased. SLM floating microspheres with normal

frequency distribution were obtained.

Entrapment efficiency increase with increase in the polymer concentration. From

the results it can be inferred that there was a proper distribution of SLM in the

microspheres and the deviation was within the acceptable limits.

The study also indicated that the amount of drug release decreases with an

increase in the polymer concentration. The in vitro performance of SLM floating

microspheres showed prolonged and controlled release of drug.

7. CONCLUSION

CHAPTER 7 CONCLUSION


The co-efficient of determination indicated that the release data was best fitted

with zero order kinetics. Higuchi equation explains the diffusion controlled

release mechanism. The diffusion exponent ‘n’ values of Korsemeyer-Peppas

model was found to be in the range of 0.5 to 1 for the SLM floating microspheres

prepared with HPMC E 50 LV and EC indicating Non-Fickian of drug through

SLM floating microspheres.

The DSC data indicates that the SLM is still present in its lattice structure in the

physical mixture where as it was completely amorphous inside the SLM floating

microspheres. This may be due to the conditions used to prepare the SLM floating

microspheres lead to cause complete SLM amorphization. The melting point of

the SLM was estimated by open capillaries and found agrees well with the DSC

data.

From the study it is evident that promising controlled release floating

microspheres of SLM may be developed by solvent evaporation techniques by

using polymers like HPMC E 50 LV and EC. However, from all the data analysis

the formulation SLM3 found to be the most ideal batch .

CHAPTER 8 SUMMARY


The goal of present work is to provide a therapeutic amount of SLM to the

proper site in the body and also to achieve and maintain the desired SLM

concentration. SLM, has a half life of (4-6hrs) and it reaches a peak plasma

concentration after 1h.It is highly soluble in methanol and 0.1M HCL (11.803 mg/ml)

and solubility decreases with increasing pH over the physiological range, which

makes SLM as a suitable candidate for FDDS in order to prolong the gastric residence

time.

An attempt was made to prepare microspheres of SLM floating o/w emulsion

solvent evaporation techniques by using polymers like HPMC E 50 LV and EC

achieve an oral controlled release of the SLM. In the present study six formulations

were formulated by using HPMC E 50 LV and EC in various proportions.

In pre formulation study, estimation of SLM was carried out by Shimadzu UV

spectrophotometer at λ max 287 nm using Methanol as solvent, which had a good

reproducibility and this method was used in entire study.

All the formulations were subjected for evaluation. Results of preformulation

studies, FTIR, SEM, particle size and size distribution, % yield, drug content,

buoyancy time and entrapment efficiency, in vitro dissolution and release kinetics,

DSC had shown satisfactory results.

The FTIR Spectra revealed that, there was no interaction between polymers and

SLM. The polymers were compatible with the SLM. Surface smoothness of the SLM

floating microspheres was increased by increasing the polymer concentration, which

was confirmed by SEM. As the polymer ratio was increased, the mean particle size of

8. SUMMARY

CHAPTER 8 SUMMARY


SLM floating microspheres was also increased. SLM floating microspheres with

normal frequency distribution were obtained. Entrapment efficiency was increased

with increased polymer concentration. From the results it can be inferred that there

was a proper distribution of SLM in the microspheres and the deviation was within

the acceptable limits.

On the basis of release data and graphical analysis formulation SLM6 showed a

good controlled release profile with maximum entrapment efficiency because of high

polymer concentration. The co-efficient of determination indicated that the release

data was best fitted with zero order kinetics. Higuchi equation explains the diffusion

controlled release mechanism. The diffusion exponent ‘n’ values of Korsemeyer-

Peppas model was found to be in the range of 0.5 to 1 for the SLM floating

microspheres prepared with HPMC E 50 LV and EC indicating Non-Fickian of drug

through SLM floating microspheres.

The DSC data indicates that the drug is still present in its lattice structure in the

physical mixture where as it is completely amorphous inside the SLM floating

microspheres. This may be due to the conditions used to prepare the SLM floating

microspheres lead to cause complete drug amorphization. The melting points of the

SLM was estimated by open capillaries and found agrees well with the DSC data.

Hence, from the above obtained data it can be summarized that it is possible to

formulate promising controlled release floating microspheres of SLM by solvent

evaporation technique using polymers like HPMC E 50 LV and EC.

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CHAPTER 10 ANNEXURES


List of publications

Review article

1) Sivanagaraju Thati*, Ganesh N.S., Floating drug delivery system: An emerging

trend. Indian Journal of Pharmaceutical Sciences. (Communicated).

Research article

1) Sivanagaraju Thati*,

Ganesh N.S. Formulation and evaluation of floating

microspheres of Silymarin for enhanced bioavailability. Research Journal of

Pharmaceutical, Biological and Chemical Sciences (Communicated).

2) Sivanagaraju Thati*,Ganesh N.S., Chintalapali Rajesh .Effect of damar gum in

the development of microspheres containing a herbal hepatoprotective drug

Silymarin.(Communicated to 64th

Indian Pharmaceutical Congress Chennai).

10. ANNEXURES

FORMULATION AND EVALUATION OF FLOATING …

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