MUCOADHESIVE AGENTS

INTRODUCTION

Most of the medicinal resource of India is from natural source. Due to modern

advances in technology the dosage form could deliver the medicines of either natural,

synthetic or else for days to years, oral drug delivery has been known for decades as

the most widely utilized route of administration among all the routes that have been

explored for the systemic delivery of drugs. The reasons that the oral route achieved

such popularity may be impart attributed to its ease of administration as well as the

traditional belief that by oral administration the drug is as well absorbed as the food

stuffs that are ingested daily.

DEFINITION

Mucoadhesives are synthetic or natural polymers, which interact with the mucus layer covering the mucosal epithetical surface and mucin molecules constituting a major part of mucus.

SIGNIFICANCE

The aim of this investigation was to prepare microemulsions containing zolmitriptan

(ZT) for rapid drug delivery to the brain to treat acute attacks of migraine and to

characterize microemulsions and evaluate biodistribution in rats. Zolmitriptan

microemulsions (ZME) were prepared using the titration method and were

characterized for globule size distribution and zeta potential

ABSTRACT

The aim of the investigation was to prepare and characterize

microemulsion/mucoadhesive microemulsion of tacrine (TME/TMME), assess its

pharmacokinetic and pharmacodynamic performances for brain targeting and for

improvement in memory in scopolamine-induced amnesic mice. The TME was

prepared by the titration method and characterized. Biodistribution of tacrine solution

and formulations after intravenous and intranasal administrations were evaluated

using 99mTc as marker. From the data, the pharmacokinetic parameters, drug targeting

efficiency, and direct nose-to-brain drug transport were calculated.

1

CLASSIFICATION

Drug targeting can be classified on the basis of the level of selectively obtained on

the delivery process.

FIRST ORDER OF TARGETING(ORGAN TARGETING)

It refers to the restricted distribution of drug carrier complex to the capillary

bed of the site or action (Organ or tissues). ETIN

SECOND ORDER OF TARGETING (CELLULAR TARG G)

It refers to the selective delivery of the drug carrier complex to specific cell.

EXAMPLE: TUMOR CELLS.

1 THIRD ORDER OF TARGETING (SUB-CELLULAR TARGETING)

It refers to the carrier directed release of drug at selected intracellular sites.

EXAMPLE: LYSOSOMES

CONTROLLING OF GIT TRANSMIT

To control and to prolong the GIT transmit of oral controlled delivery system for all

kind of drugs are through the polymers mainly, and the polymers may be of either

natural or synthetic.Hence it may be emphasized that the polymers are playing a key

role in all types controlled/ sustained release dosage formulations and requires almost

importance in selection of polymers, which should be therapeutically and chemically

insert so that the untoward effects may not occur when administered into the human

system(Paul Enrich.et.al)The main objective of this is, polymers can be used to over

come physiological barriers in long-term drug delivery.

2

MUCOADHESION DRUG DELIVERY SYSTEM

Mucoadhesion in drug delivery systems has recently gained interest among

pharmaceutical scientists of promoting dosage form residence time as well as

improving intimacy of contact with various absorptive membranes of the biological

system (Wong, L.F. et.al).The concept of mucosal adhesives or Mucoadhesives, was

introduced into the controlled drug delivery are in the early 1980s (ALKa Ahuja

et.al)Mucoadhesives are synthetic or natural polymers, which interact with the mucus

layer covering the mucosal epithetical surface and mucin molecules constituting a

major part of mucus.

THE MUCOADHESIVE DRUG DELIVERY SYSTEM MAY INCLUDE THE FOLLOWING

BUCCAL DELIVERY SYSTEM

1. Sublingual Delivery system

2. Vaginal delivery system

3. Rectal delivery system

4. Nasal delivery system

3

MUCOADHESIVE STUDIES

To characterize the mucoadhesive strength, the detachment force method was

used. Mouth of a glass vial fixed with a fresh section of animal tissue from fundus

portion of goat intestine, facing mucosal side out and kept in simulated gastric fluid

(pH 1.2) without pepsin. Kept another portion of mucus side of exposed tissue over a

rubber stopper and secured with an aluminum cap. The mucoadhesive tablet placed on

the exposed mucus layer (later case), kept in contact with the former tissue which is

connected with a pan in which the weight can be raised. At specific intervals, applied

weight and the force required to detach measured for mucoadhesive strength.

The shear stress measures the force that causes a mucoadhesive to slide with respect

to the mucus layer in a direction parallel to their place of contact of adhesion. The test

was done by coating either side of the two slides with natural adhesive agent followed

by the second layer coated with mucous layer. Mucus forms thin film between the two

natural adhesive coated slides the test measures the force required to separate the two

surfaces. In present study was used weight with reference to force. calculate using the

formula:

A small glass plate (2Χ5cm) was coated with 1% w/v of the mucoadhesive agent.

The mucus gel was taken from goat intestine kept in a suitable container, where the

above-mentioned glass plate can be kept in contact with gel in a balanced condition

and the temperature was maintain at 30° C. Nylon thread was attached at one end of

the glass plate. Provision was given to raise the weight (4) at the other end. At

specified intervals, weight was added to detach the coated glass plate (2) from gel and

the force required to pull the plate out of the gel (3) was determined under

experimentalcondition.

PREPARATION OF MUCOADHESIVE TABLET

Theophylline mucoadhesive tablets were prepared using Cadmach; tablet machine by the wet

granulation technique. The drug to adhesive agent ratio used was1:1, 1:2 and 1:3 .

4

IN VITRO RELEASE STUDY

The in vitro release studies of theophylline 100 mg oral mucoadhesive tablet were

carried out according to U.S.P apparatus 2 (paddle method). 100 mg tablets were

taken in 900 ml of acidic buffer (pH 1.2) maintained at 37° C and rotated at 50 rpm.

At specific time intervals 5 ml of the sample withdrawn from the dissolution media

and equal volume of media was replaced immediately. Withdrawn samples were

filtered, suitably diluted and analyzed spectrophotometrically at 272 nm.

IN VIVO BIO ADHESIVE STUDY

To study the bioadhesive character and mean residence time of the natural polymer in

the stomach, barium sulphate loaded tablet was used. Two healthy rabbits weighing

2.5 kg were selected and administered orally with the tablet. X-ray photograph was

taken at different time intervals shown in the . (Animal ethical committee No: JSSCP/

IAEC/ M.PHARM/ PH. CEUTICS/ 05/ 2007 - 2008.)

Mucoadhesion is the relatively new and emerging concept in drug delivery.

Mucoadhesion keeps the delivery system adhering to the mucus membrane.

Transmucosaldrug delivery systems show various merits over conventional drug

deliversystem. Mucoadhesive polymers facilitate the mucoadhesion by their specific

properties.This article reviews desirable properties of mucoadhesive polymers and the

latest advancement in the field.

5

6

DEVELOPMENT OF DRUGS DELIVERY SYSTEM

In recent years, considerable attention has been focused on the development of new

drug delivery system. There are a number of reasons for the intense interest in new

system. First one is possibility of repeating successful drugs by applying the concepts

on techniques of controlled released drug delivery system. Second one is the need to

deliver the novel. Numerous oral delivery systems have been developed to act as

drugs reservoirs from which the active substance is released over a defined period of

time at a predetermined and controlled rate. From a pharmacokinetic point of view,

the idea of sustained and controlled release dosage forms should be comparable to an

intravenous infusion, which continuously supplies the amount of drug needed to

maintain constant plasma level once the steady state is reached.

GASTRO INTESTINAL TRANSIT OF DRUG DELIVERY SYSTEM.

Gastric Emptying

After ingestion, an oral no disintegrating dosage form will stay in the stomach for an

unpredictable period of time. (A. J. Moes. Et.al.). the role of the stomach in terms of

its anatomical structure and motor functioning during either inter digestive or

digestive phase.During inter digestive phase, the fasted stomach exhibits a cyclic

activity called inter digestive migrating motor complex (IMML). Each cycle can be

divided into four phases as follows.

Phase-I

The most quiescent, develops few or no contractions during 45 to 60 min.

Phase-II

The Incidence of irregular and intermittent sweeping contractions gradually increases,

culminating in the onset of phase III.

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IMPORTANT FACTORS OF MUCOADHESION

High molecular weight (up to 100,000), High viscosity (up to an optimum),

Long chain polymers, Optimum concentration of polymeric adhesive, Flexibility

of polymer chain, Spatial confirmation, Optimum cross-linked density of polymer,

Charge and degree of ionization of polymer (anion >cation >unionized),

Optimum medium pH, Optimum hydration of the polymer, High applied strength

and duration of its application and High initial contact time, are some basic

properties which a polymer must have to show a good mucoadhesive profile20. The

physiochemical properties of the mucus are known to change during diseases

conditions such as common cold, gastric ulcers, ulcerative colitis, cystic

fibrosis, bacterial and fungal infections of the female reproductive tract and

inflammatory conditions of the eye, thereby changing the degree of mucoadhesion.

8

The focus of pharmaceutical research is being steadily shifted from the

development of new chemical entities to the development of novel drug delivery

system (NDDS) of existing drug molecule to maximize their effective in terms of

therapeutic action and patent protection1,2. Moreover the

development of NDDS are going to be the utmost need of pharmaceutical industry

especially after enforcement of Product Patent3,4.The development of NDDS has been

made possible by the various compatible polymers

to modify the release pattern of drug5,6. In the recent years the

interest is growing to develop a drug delivery system with the use of a mucoadhesive

polymer that will attach to related tissue or to the surface coating of the

tissue for the targeting various absorptive mucosa such as ocular, nasal,

pulmonary, buccal, vaginal etc. This system of drug delivery is called as

mucoadhesive drug delivery system.

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NEXT GENERATION MUCOADHESIVE POLYMERS

With the disappointment in the merger

of mucoadhesive systems into pharmaceuticals in the site-specific drug delivery

area, there has been an increasing interest from researchers in targeting

regions of the GIT using more selective compounds capable of distinguishing

between the types of cells found in different areas of the GIT. Loosely termed

“cytoadhesion,” this concept is specifically based on certain materials that

can reversibly bind to cell surfaces in the GIT22. These next

generation of mucoadhesives function with greater specificity because they are

based on receptor-ligand-like interactions in which the molecules bind strongly

and rapidly directly onto the mucosal cell surface rather than the mucus itself .One

these unique requirements is called lectins. Lectins are proteins or

glycoproteins and share the common ability to bind specifically and reversibly

to carbohydrates. They exist in either soluble or cell-associated forms and

possess carbohydrate-selective and recognizing parts. They are found mostly in

plants, to a lesser extent in some vertebrates (referred to as endogenous

lectins), and can also be produced from bacteria or invertebrates24.

Lectin-based drug delivery systems have applicability in targeting epithelial

cells, intestinal M cells, and enterocytes. The intestinal epithelial cells

possess a cell surface composed of membrane-anchored glycoconjugates. It is

these surfaces that could be targeted by lectins, thus enabling an intestinal

delivery concept.One lectin which has been studied to

considerable extent in vitro binding and uptake is tomato lectin (TL),

which has been shown to bind selectively to the small intestine epithelium. In

one study, using the everted gut sac model, this lectin was bound to

polystyrene microspheres. Uptake of (TL) into the serosal fluid was reported as

eight-fold higher than the control (BSA)25. Furthermore,

BSA-coupled microspheres were shown to have slower uptake than TL-coupled

microspheres by a factor of two. In another study, specific binding by tomato

lectin-coated polystyrene microspheres (0.98 mm) to enterocytes in vitro was

examined26. fluorescently labelled polystyrene microspheres were

coated with TL, and incubated in a CaCo-2 cell line. It was observed that the

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lectin-coated microspheres were resistant to repeat washings compared to the

control (BSA-microsphere).For optimal buccal mucoadhesion, Shojaei and Li have

designed,synthesizedand characterized a copolymer of PAA and PEG monoethylether

monomethacrylate(PAA-co-PEG).

(PEGMM)27. By adding PEG to these polymers, many of the shortcomings

of PAA for mucoadhesion, outlined earlier, were eliminated. Hydration studies,

glass transition temperature, mucoadhesive force, surface energy analysis

and effect of chain length and molecular weight on mucoadhesive force were

studied. The resulting polymer has a lower glass transition temperature than

PAA and exists as a rubbery polymer at room temperature. Copolymers of 12

and 16-mole% PEGMM showed higher mucoadhesion than PAA. The effects of

hydration

on mucoadhesion seen by the copolymers revealed that film containing lower

PEGMM content, which had higher hydration levels, had lower mucoadhesive

strengths.. Polymers investigated in this study also showed that

the molecular weight and chain length had little or no effect on the mucoadhesive

force.Lele, et al, investigated novel polymers of PAA

complexed with PEGylated drug conjugate29. Only a carboxyl group

containing drugs such as indomethacin could be loaded into the devices made

from these polymers. An increase in the molecular weight of PEG in these

copolymers resulted in a decrease in the release of free indomethacin,

indicating that drug release can be manipulated by choosing different molecular

weights of PEG.

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FORMULATION AND EVALUTION OF MUCOADHESIVE

DETERMINATION OF MUCOADHESIVE FORCE:

The mucoadhesive force of organogel onvaginal mucosal tissues was determined

by means of mucoadhesive force measuring apparatus, fabricated in our laboratory.

Vaginal mucosal tissues were removed from Sprague-Dawley ratsand tissue were

stored frozen in phosphate buffer at pH 5.5, and thawed to the room temperature

before use. At the time of testing, a section of tissue was secured (keeping the

mucosal side out) to the upper side of a glass vial using a cyanoacrylate adhesive. The

diameter of each exposed mucosal membrane was1.5 cm. The vials were equilibrated

and maintained at 37° for 10 min. One vial with a section of tissue was connected to

the balance and the other vial was fixed on a height adjustable pan. To the exposed

surface of the tissue attached on the vial, a constant amount of 0.1 g organogel was

applied. Before applying the organogel, 150 μl of simulated vaginal fluid was evenly

spread on the surface of the test membrane. The height of the vial was adjusted such

that the organogel could adhere to the mucosal surface of both vials. Immediately, a

constant force of 0.5 N (Newton) for 2 min was applied to ensure intimate contact

between the tissue and the sample. The upper vial was then moved upwards at a

constant force, while it was connected to the balance. Weights were added at a

constant rate to the pan on the other side of the modified balance until the two vials

were separated.The mucoadhesive force, expressed as the detachment stress in

dynes/cm2, was determined from the minimal weights needed to detach the tissues

from the surface of each formulation, using the following Eqn.

Detachment stress (dynes/cm2) = (m×g)/a,

Where ‘m’ is the weight added to the balance in grams; ‘g’ is the acceleration due to

gravity taken as 980 cm/s2; and ‘a’ is the area of tissue exposed.Effect of varying

contact time (1, 2, 3, 5 and 10 min) was investigated for some of the organogel

preparations to optimize initial contact time. In brief, formulations were allowed to be

in contact with mucosa for carrying contact time (1, 2, 3, 5, and 10 min.), and the

mucoadhesive force was determined as discussed above

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MEASUREMENT OF VISCOSITY OF ORGANOGELS:

Viscosity determinations of the prepared organogels were carried out by cone and

plate geometry viscometer (Model: RV DV-E 230), using spindle No 7. Viscosity of

organogels was measured at 10 rpmat a temperature of 25°C[24].The averages of three

readings were used to calculate the viscosity. Evaluations were conducted in

triplicate.

SPREADABILITY:

For the determination of spreadability, excess of sample was applied between

the two glass Slides and was compressed to uniform thickness by placing 1000 g

weight for 5 min. Weight (50g) was added to the pan. The time required to separate

the two slides, i.e. the time in which the upper glass slide moves over the lower plate

was taken as measure of spreadability (S)[25]. S=M×L/T,

Where M = weight tide to upper slide, L = length moved on the glass slide, T

= time taken.

GELLING CAPACITY:

The gelling capacity was determined by placing a drop of the system in a vial

containing 2 ml of simulated vaginal fluid (pH 5.5) freshly prepared and equilibrated

at 37°Cand visually assessing the organogel formation and noting the time for

gelation and thetime taken for the organogel formed to dissolve. Different grades

were allotted as per the organogel integrity, weight and rate of formation of organogel

with respect to time.

IN VITRO RELEASE STUDIES:

The in vitro release of from different formulations was determined using a dialysis

bag placed in a sealed glass vial under constant magnetic stirring. The gel

formulations (2.5 g) were packed into the dialysis bags (Spectra/Por Cellulose

EsterMembrane MWCO: 100 000 Da, Spectrum Labs, Rancho Dominguez, CA)

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sealed with closures of 50 mm (Spectrum Labs). The release medium was 100 mL

0.1M citrate-phosphate buffer (pH 5.5) containing 1% Tween 80, providing sink

conditions for clotrimazole. The medium was maintained at 37ºC and stirred at 100

rpm. At various time intervals, 5 mL of dissolution fluid was collected. Levels of

clotrimazole in the samples were analyzed with a Shimadzu UV-VIS 1760A

spectrophotometer at λ = 262 nm. The exact amount of clotrimazole released from the

formulation was calculated with a calibration curve with an analytically validated

method (r2 =0.9958, repeatability coefficient of variation (CV) = 0.11%,

reproducibility CV = 2.2%).

ANTIFUNGAL EFFICACY STUDIES:

The antifungal efficacy study against Candida albicans was determined by agar

diffusion method employing ‘cup plate technique’. Sterile solutions of CT in DMSO

(standard solution) and the developed organogel having the pH adjusted to 7.0 were

poured into cups (0.1 ml of 0.1% w/v) bored into sterile malt yeast agar previously

seeded with test organism. After allowing diffusion of the solutions for 2 h, the agar

plates were incubated at 37°Cfor 48 h. The zone of inhibition (ZOI) was measured

and compared with that of pure drug. The entire operation was carried out in aseptic

condition throughout the study. Each solution was tested in triplicate. Both positive

and negative controls were maintained throughout the study[26].

RESULTS AND DISCUSSION

The organogel formulations were optimized by factorial design method (using

Design Expert software). Concentration of Soya lecithin, Pluronic F 127 and

Carbopol 934, were three factors selected for optimization of formula.Compositions

of various formulations used in the prepared PLOs are given in table 1.

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TABLE 1: COMPOSITION OF VARIOUS FORMULATIONS

Formulation

Clotrimazole

(%)

Soya Lecithin (%)

Carbopol 934 (%)

Pluronic F127 (%)

Isopropyl myristate upto

(ml)

Sorbic acid (%)

Water upto (ml)

F1 1 2 0.8 50 100 0.2 100

F2 1 2 0.8 32.5 100 0.2 100

F3 1 2 0.2 15 100 0.2 100

F4 1 2 1.4 50 100 0.2 100

F5 1 4 1.4 50 100 0.2 100

F6 1 4 1.4 15 100 0.2 100

F7 1 4 0.2 15 100 0.2 100

F8 1 4 0.2 50 100 0.2 100

F9 1 6 0.8 50 100 0.2 100

F10 1 6 0.8 15 100 0.2 100

F11 1 6 0.2 32.5 100 0.2 100

F12 1 6 1.4 32.5 100 0.2 100

The prepared PLOs formulations were characterized on the basis of spreadibility,

rheological behavior, drug content (%), mucoadhesive force, gelling capacity and in-

vitro release profiles. The prepared PLOs formulations were white to pale yellow

viscous creamy preparation with a smooth and homogeneous appearance. The pH

values of all prepared formulation ranged from 5.5 to 6.5, which is considered

acceptable to avoid the risk of irritation upon application to the skin as pH of skin

5.5.The values of spreadability indicate that the organogel is easily spreadable by

small amount of shear. The spreadability of all formulations from 10.01 to 13.1.

Viscosity determinations of the prepared organogels were carried out by cone and

plate geometry viscometerusing spindle No 7. The highestviscosity was found in

organogel contain high level of the Cabopol 934 concentration.The drug content in

organogel was found in range of 92.8 % to 99.7 %. The higher drug content found in

F11 i.e. 99.7% due to the optimum concentration of pluronic F127 and soya lecithin.

The in vitro release profiles of clotrimazole from its various organogel. formulations

are represented in Table 3. Higher drug release was observed with formulations F11.

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This finding may be due to presence of optimum level of carbopol 934 (1%) and soya

lecithin (4%). Further increase in concentration of lecithin decreased cumulative %

drug release which might be due to extensive formation of network like structure with

very high viscosity One lectin which has been studied to

considerable extent in vitro binding and uptake is tomato lectin (TL),

which has been shown to bind selectively to the small intestine epithelium. In

one study, using the everted gut sac model, this lectin was bound to

polystyrene microspheres. Uptake of (TL) into the serosal fluid was reported as

eight-fold higher than the control (BSA)25. Furthermore,

BSA-coupled microspheres were shown to have slower uptake than TL-coupled

microspheres by a factor of two. In another study, specific binding by tomato

lectin-coated polystyrene microspheres (0.98 mm) to enterocytes in vitro was

examined26. fluorescently labelled polystyrene microspheres were

coated with TL, and incubated in a CaCo-2 cell line. It was observed that the

lectin-coated microspheres were resistant to repeat washings compared to the

control (BSA-microsphere).

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MATERIALS AND METHODS

MATERIALS

Poly(methylvinylether-co-maleic anhydride) (Gantrez S97) and polyvinylpyrollidone

(Plasdone K-90, Mv 1.3 M) were kindly donated by International Specialty Products

(Ohio, U.S.A.). Hydroxyethylcellulose (Natrosol 250-HHX-Pharm, Mv 1.3 M, DS

2.0) and polycarbophil (Noveon AA1, a divinyl glycol cross-linked poly(acrylic acid))

were also kindly donated by Aqualon (Warrington, U.K.) and Noveon Pharma GmbH

& Co KG (Raubling, Germany), respectively. Pluronic (Lutrol F127, a copolymer of

polyoxyethylene and polyoxypropylene, Mv 12600) was purchased from BTC

Specialty Chemical Distribution Limited (Cheshire, U.K.). Erioglaucine disodium salt

(792.85 MW) was purchased from Sigma (Poole, Dorset, U.K.). Replens was supplied

by AAH Hospital Service (Belfast, U.K.). Replens is a commercially available

vaginal moisturizer containing carbomer 934P, glycerin, hydrogenated palm oil

glyceride, mineral oil, polycarbophil, purified water, and sorbic acid. All other

chemicals were purchased from Sigma (Poole, Dorset, U.K.) and were of AnalaR

grade or equivalent quality.

PREPARATION OF RHEOLOGICALLY STRUCTURED VEHICLES (RSV)

Sorbic acid (0.1% w/w) and the required amount of sodium hydroxide to achieve a

final pH = 6 were added to water in a HiVac mixing bowl (Summit Medical,

Gloucestershire, U.K.). The mucoadhesive component, polycarbophil or

poly(methylvinylether-co-maleic anhydride) (PC or Gantrez; 3% w/w), was

subsequently introduced and mixed under vacuum. Following complete dissolution of

the mucoadhesive component, Pluronic F127 (PL; 0 or 10% w/w),

hydroxyethylcellulose (HEC; 5% w/w), and polyvinylpyrrolidone (PVP; 4% w/w)

were added in a stepwise fashion and mixed under vacuum. To remove all entrapped

air, formulations were transferred to McCartney bottles, gently centrifuged, and stored

at 4 °C for 48 h prior to testing. Formulations containing erioglaucine (100 μg per 3 g

dose) were prepared using a similar method with the exception that erioglaucine was

added to the aqueous phase (1.36 mL of 11.18 mg/mL) prior to addition of F127.

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PREPARATION OF SIMULATED VAGINAL FLUID

For the purposes of gel dilution studies, simulated vaginal fluid (SVF) was prepared

as described by Owen and Katz.(14) NaCl (3.51 g), KOH (1.40 g), Ca(OH)2 (0.222 g),

bovine serum albumin (0.018 g), lactic acid (2 g), acetic acid (1 g), glycerol (0.16 g),

urea (0.4 g), and glucose (5 g) were dissolved in 1 L of deionized water, followed by

adjustment to pH 4.2 with HCl.

IN VITRO EVALUATION OF MUCOADHESION

The mucoadhesive properties of RSVs were determined using a TA-XT2 Texture

Analyzer (Stable Microsystems, Surrey, England) and a previously described mucin

disk test.(15) In summary, porcine mucin discs (250 mg, 13 mm diameter), prepared

by direct compression (10 tonne, 30s), were horizontally attached onto the lower face

of an inert horizontal polycarbonate probe and immersed in a mucin solution (5%

w/w) for 30s. The mucin disk was brought into contact with the formulation under

examination and a force of 1 N was then applied for 30 s to ensure intimate contact

between the disk and formulation.

MEASUREMENT OF WORK OF SYRINGEABILITY

The work done to expel formulations from a model vaginal applicator was determined

using a TA-XT2 Texture Analyzer in compression mode. RSVs (3 g) were packed

into a model applicator and an inert polycarbonate probe was used to expel the

syringe contents at a rate of 2.0 mm/s through a distance of 30 mm. The work done to

expel the syringe contents was calculated from the area under the resultant force-time

plot. In addition to RSVs, a commercially available formulation, Replens was also

studied for comparison purposes.

TEXTURE PROFILE ANALYSIS (TPA)

The compressional flow (hardness and compressibility) properties of RSV

formulations were determined using a TA-XT2 Texture Analyzer in compression

mode, as described previously.(15) In brief, samples (16 g) were packed into identical

McCartney bottles and centrifuged to remove entrapped air. An analytical probe (10

mm diameter) was compressed twice into each formulation at a defined rate (2 mm/s)

to a defined depth (15 mm), allowing a 15 s delay period between the end of the first

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and beginning of the second compression. From the resultant force-time plot the

mechanical parameters including hardness (the force required to attain a given

deformation) and compressibility (the work required to deform the formulation during

the first compression of the probe) were derived.

RHEOLOGICAL (DYNAMIC) ANALYSIS

Oscillatory (dynamic) rheometry was conducted using an AR2000 rheometer (T.A.

Instruments, Surrey, England) at 25 ± 0.1 °C using a 2 cm diameter parallel plate

geometry and a gap of 1000 μm, as previously reported.(16) Samples were carefully

applied to the lower stationary plate and the upper plate was adjusted to the

predefined gap size. Formulations were then retained for an equilibrium period to

facilitate relaxation of internal stresses introduced during sample loading. During

testing, samples were subjected to a predetermined oscillatory stress value (selected

from within the linear viscoelastic region) over a frequency range from 0.1 to 10 Hz.

Calculation of the storage modulus (G′), loss modulus (G′′), loss tangent (tan δ), and

dynamic viscosity (n′) were performed using proprietary software (TA Instruments,

Leatherhead, England).

IN VITRO GEL DILUTION

Given that vaginal semisolids will experience dilution in vivo it is important to

characterize this effect by dilution of the prepared RSVs with simulated vaginal fluid

(SVF). In summary, a defined mass (3 g) of RSV was thoroughly mixed in a HiVac

mixing bowl (Summit Medical, Gloucestershire, U.K.) with 0.1, 0.3, 0.5, 0.7, and 0.9

mL of SVF. Gels were transferred to McCartney bottles, gently centrifuged to remove

entrapped air and storage at +4 °C for 24 h prior to dynamic rheological analysis (37

°C). The dilution ratio was selected to represent that normally encountered in the

vagina following insertion of the delivery vehicle.(17)

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FLOW ANALYSIS UNDER CONTINUOUS SHEAR

Flow rheometry was conducted at 25 ± 0.1 °C using an AR 2000 rotational rheometer

operating in continuous flow mode using a parallel plate and a constant gap of 1000

μm. Sample geometry (2, 4, or 6 cm plate) was selected according to formulation

consistency. Flow rheology was conducted using a loop test in which the shearing rate

was increased gradually from a minimum (0.001 s−1) up to a predetermined maximum

(2 s−1) within 60 s and then returned to the starting shear rate under the same

conditions. For comparison purposes, the commercially available vaginal gel,

Replens, was also studied. Modeling of the flow properties of the various

formulations was performed using the Ostwald-de Waele equation, as follows:

where σ is the shearing stress, is the rate of shear, k is the consistency, and n is the

pseudoplastic index.

IN VITRO RELEASE OF ERIOGLAUCINE FROM RSVS

A defined mass (5 g, n = 6) of each formulation was placed in a cylindrical vessel and

anchored at the bottom of a stoppered 100 mL glass vial containing 50 mL of SVF,

and the glass containers were placed in a shaking orbital incubator (Sanyo

Gallenkamp, 100 rpm) maintained at 37 °C. The release medium was sampled (7 mL)

at predetermined time intervals and analyzed by UV spectroscopy at 630 nm. At each

sample point an equal volume of fresh prewarmed dissolution media was added to the

dissolution vessels to replace the volume sampled. The mass of erioglaucine (EG)

released was calculated with reference to a calibration curve (concentration range 0−8

mg/mL, r > 0.999).

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OTHER FACTORS INFLUENCING GASTRIC EMPTYING

Numerous other factors may influence the gastric transit of sustained release dosage

forms. Among the stimulatory and inhibitory mechanisms that regulate the emptying

rate of meal, the characteristics of the diet components have to first be taken into

account first. These include acidity, osmolality , temperature, viscosity, volume,

caloric contents and relative fat, protein and carbohydrate concentrations(A.J. Moes

et. al).

PROLONGATION OF THE GASTRIC RESIDENCE OF DOSAGE

FORMS.

From the theoretical point of view, these instances are few and mainly depend on the

characteristics of the drug substances.

Examples

1. Poorly acid soluble drugs may show dissolution problems in gastric fluids.

2. Drugs that are unstable and destroyed in the gastric environment.

3. Corticosteroids and 5-amino salicylic acid, specifically designed oral forms may

prove superior to rectal preparation in as much as small intestine release can be

avoided.

21

DRUG TARGETING

Paul Enrich first introduced the Concept of drug targeting by (10990), when he had

been reported, which can deliver a drug selectively to the desired site of action

without harming the non-target organs or tissues. Drug targeting can be defined as the

ability to direct a therapeutic agent specifically to the desired site of action with little

or no interaction with target tissues. (Paul Enrich, et.al)

THE DRUG TARGETING INCLUDES,

The ability to reach specific cells or diseased site in the body with concomitant reduction in the dose and side effects.

1. To reach previously unacceptable sites.2. To protect the drug and the body from one another until the desired site of

action is reached.3. To control the frequency of drugs dosing to pharmaceutical receptors.

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USE OF MUCOSAL ADHESIVE PREPARATIONS

The drug absorption is limited by the residence time of the drug at the absorption site.

For example, in ocular drug delivery, less than 2mts are available for drug absorption

after instillation of a drug solution into the eye, since it is removed rapidly by solution

drainage, hence the ability to extend contact time of an ocular drug delivery system in

front of the eye would undoubtedly improve drug bioavailability.In oral drug delivery,

the drug absorption is limited by the gastrointestinal transit time of the dosage form.

Since many drugs are absorbed only form the upper small intestine, localizing oral

drug delivery systems in the stomach or in the duodenum would significantly improve

the extent of drug absorption. The mucus layer, which covers the epithelial surface,

has various roles.

1. PROTECTIVE ROLE

The Protective role results particularly from its hydrophobicity and protecting the

mucosa from the lumen diffusion of hydrochloric acid from the lumen to the epithelial

surface.

2. BARRIER /ROLE

The mucus constitutes diffusion barrier for molecules, and especially against drug

absorption diffusion through mucus layer depends on molecule charge, hydration

radius, ability to form hydrogen bonds and molecular weight.

3. ADHESION ROLE

Mucus has strong cohesive properties and firmly binds the epithelial cells surface as a

continuous gel layer.

4. LUBRICATION ROLE

The mucus layer keeps the mucosal membrane moist. Continuous secretion of mucus

from the goblet cells is necessary to compensate for the removal of the mucus layer

due to digestion, bacterial degradation and solubilisation of mucin molecules.

23

MUCOADHESION

One of the most important factors for bioadhesion is tissue surface roughness.

Castellanos et.al(1) showed that adhesive joints may fail at relatively low applied

stresses if cracks, air bubbles, voids, inclusions or other surface defects are present.

Viscosity and wetting power are the most important factors for satisfactory

bioadhesion.

THEORIES OF BIOADHESION

Several theories have been proposed to explain the fundamental mechanisms of adhesion. They are,

Electronic Theory

Adsorption Theory

Wetting Theory

Diffusion Theory

Fracture Theory

1. ELECTRONIC THEORY

Electron transfer occurs upon contact of an adhesive polymer with a mucus

glycoprotein network because of difference in their electronic structures. This results

in the formation of an electrical double layer at the interface. Adhesion occurs due to

attractive forces across the double layer.

2. ADSORPTION THEORY

After an initial contact between two surfaces, the material adheres because of surface

acting between the atoms in the two surfaces.

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3. WETTING THEORY

It is predominantly applicable to liquid bioadhesive systems. It analyses adhesive and

contact behavior in terms of the ability of a liquid or paste to spread over a biological

systems.

4. DIFFUSION THEORY

The Polymers chain and the mucus mix to a sufficient depth to create a semi

permanent adhesive bond. The exact depth to which the polymer chains penetrate the

mucus depends on the diffusion co-efficient and the time of contact.

5. Fracture Theory

In this theory, attempted to relate the difficulty of separation of two surfaces after

adhesion. Fracture theory equivalent to adhesive strength is given by,

G = (È € I L )1/2

È = Young's Modulus of elasticity

€ = Fracture energy

L = Critical crack length

25

AIM AND SCOPE OF WORK

Mucoadhesives are synthetic or natural polymers or agents, which interact with the

mucus, layer covering the mucosal epithelial surface and mucin molecules

constitutioning the major part of mucus.The adhesives firmly stick to the mucosal

surface and prolonged its gastric residential time, until removes it over of

mucin. Most of the routes of drug administration such as ocular, nasal, buccal,

respiratory, gastrointestinal, rectal and gaginal route are coated with mucus layer,

mucoadhesive are expected to increase the residence time. They provide intimate

contact between a dosage form and the absorbing tissue, which may result in high

drug concentration in local area and hence high drug flux through the absorbing

tissue.Furthermore, the performance of mucoadhesive can be tested by various

methods. Such as

Measurement of Bioavailability

Measurement of Residence Time

Me1asurement of Tensile Strength

Thumb test

Falling liquid film method

Mucin gold staining

The performance or the capacity of mucoadhesive can be accessed by analyzing the

parameters which will provides the degree of adhesion and the possible methods to be

studied in this laboratory are as follows.

Measurement of shear and peel strength

Wilhelmy's method

Falling sphere method

Invivo evaluation studies

26

REVIEW OF LITERATURE

A review of literature survey has been carried out through various Indian and

international journals that are view the properties and evaluation of Polymers and

related aspects. Some of the important works are revealed here. A method using

texture analysed equipment and chicken pouch as the biological tissue was evaluated

for measuring the bioadhesive properties of some polymers (Wong, C.F.et.al)Vila –

Jato, et. al., have carried out a discussion of bioadhesive systems is presented

including mucus structure, types of mucous – bioadhesion binding , the use of

bioadhesion models in the prediction of bioadhesive characteristic of a polymer, and

practical application. The tablet prepared with HPMC K4M showed greatest

bioadhesion was reported I invitro bioadhesion to rabbit intestine (Madhusudan Rao

et. AlEvaluation of mucoadhesive buccal patch for delivery of peptides and invitro

study of bioadhesives was done by Li,C.Bhatt, et.al.Minarro, et.al has carried out the

technological aspect of modified release of oral dosage form: matrix floating and

bioadhesive system.The modeling mucoadhesion by use of surface energy terms

obtained from the Lewis acid – base approach and studies on anionic, cationic and

nonionic polymers(Rillosi,et.al). Achar, L. Peppas, N.A, have carried out the

preparation characterization and mucoadhesive ineractions of Poly (methacrylic acid)

co polymers with rat mucus.Gupta, A. et.al have carried out interpolymer

complexation and its effect on bioadhesive strength and dissolution characteristics of

buccal drug delivery system.Kopecek, J.et.al has carried out the study of potential of

water-soluble polymeric carries in targeted and site specific delivery. A review of

bioadhesion/mucoadhesion polymers, assessment and determination bioadhesion

strength, mucoadhesion dosage form, equipment and methods for measuring

mucoadhesion and several controlled release mucoadhesive dosage forms are

discussed. (Gandhi et.al).Hassan, E.E. ,gallo, J.M. have studied the rheological

method for the in vitro assessment of mucin- polymer bioadhesive bond

strength. Mikos, A.G.et.al have been analysed a simple invitro method for testing and

classifying the bioadhesive behaviour or polymeric micro particle with or without

drugs is presentedReview the application of controlled released bioadhesive

formulation developed for different route of administration including oral, buccal,

nasal and vaginal etc (Garcia gonazalez, et.al)The effects of aging on the rheological,

27

dielectric and mucoadhesive properties of gel system were reported by

Tamburic,s.Craig, DQ.et.al.Drug release from oral mucosal adhesive tablets of

chitosan and sodium alginate were also reported by Miyazaki S. Nkayama et.al.In the

Invitro / ex vivo methods for evaluation of bioadhesive polymers, the apparatus for

the evaluation of bioadhesive properties of pharmaceutical polymers are described

and tested (Maggi, L.et.al).

28

DESCRIPTION OF THE POLYMERS AND CHEMICALS

HYDROXY PROPYL METHYL CELLULOSE

Hydroxy propyl cellulose is mixed alkyl hydroxyl alkyl cellolosic ether and may be

regarded as the propylene glycol ether of methyl cellulose.

Chemical name : Cellulose, 2-hydroxy propyl methyl ether.

Empirical formula : C8H15O6-(C10H8O6)-C8H15O5

Molecular weight : (Approx.) 86,000

Density : 0.25-0.70 g/cm3

PH : 6.0 – 8.0(1 % aqueous solution)

Stability : solutions are stable at PH 3.0 to 11.0

APPLICATIONS:

It is suspending, viscosity – increasing and film forming agent. It is also used as a

tablet binder and as an adhesive ointment ingredient.

RESULTS AND DISCUSSION

Mucoadhesive drug delivery system of dosage forms generally increases the

residential time of dosage forms. The extension of residential time of dosage form

mainly depends on the release rate of a drug from the core material and from the

matrix in which the drug is loaded. The release rate is mainly controlled by the

polymers and in this study, it is brought out that the natural substance, which possess

the gummy nature was subjected for evaluation studies as per the existing

literatures. The mucoadhesiveness of a sample is due to interaction between the

mucin, a glycoprotein present in the mucosa of the intestine and the drug polymer

matrix. Generally hydrophilic groups such as –OH and _NH2 groups are responsible

29

for such interactions. Most of the natural gums possess the said groups and which

may be responsible for the increase of residential time by adhering the complex or

drug matrix on the intestinal area and the slow release of drug maintains the

therapeutic effect.The observation reveals that the natural and synthetic substances

subjected fir invitro evaluations possess the bioadhesive characteristics. Among which

the natural gum obtained from Albizia odoratissima possess considerable gm of

weight was required to detach 1% w/v coated plate from the mucous gel. Among the

synthetic polymers, Carbopal NF-940 was found to possess good adhesiveness. 1.4

gm force was required to detach.

30

SUMMARY

Transmucosal drug delivery systems, are gaining popularity day by day in

the global pharma industry and a burning area of further research and development.

To summarize, polymers with certain specific characters like high molecular

weight and viscosity, long chain length, flexibility of chain length etc.

are needed for the design of transmucosal drug delivery systems.

There is no doubt that mucoadhesion has moved into a new area with these

new specific targeting compounds (Tomato lectins, Corplex™ adhesive hydrogels

etc.) with researchers and drug companies looking further into potential involvement

of more smaller complex molecules, proteins and peptides, and DNA for future

technological advancement in the ever-evolving drug delivery arena.

31

CONCLUSION

The polymers are playing an important role in the field of controlled (or)

sustained release drug delivery system. Mucoadhesives are synthetic or natural

polymers, which interact with the mucus layer covering the mucosal epithetical

surface and mucin molecules constituting a major part of mucus.As a result it will

release the drug slowly. So we get a prolong duration of action of drug.

32

BIBILIOGRAPHY

Chitnis, VS, et.al , Drug Development and Industrial pharmacy,17(6):pp 879-892.

1991.

Indian Pharmacopoeia , 1996

Craig, DQ. Et.al. Journal of Pharmacy and Pharmacology 49(Feb): pp 119 – 126,

1997.

Bio – Pharmaceutics and Pharmacokinetics a Treatise by D.M. Brahmakar and Sunil

B. Jaiswal.

Hassan.EE, et.al , Pharmaceutical Research, 7(May): pp 491-495, 1990

33

Madhusudan Rao., Y., et. al , Indian Drug, 35(sep): pp 113 – 121. 1997.

Tamburic et.al. Pharaceutical Research , 13(Feb): pp : 279-283, 1996.

Magi. L. et. al ., S.T.P. Pharma Sciences, 4(5): pp 343-348. 1994.

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