Post on 24-Jul-2015
Controlled Release Oral Drug Delivery System
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Contents
Overview of Digestive system Introduction Advantages Disadvantages
Mechanisms 1.Dissolution 2.Diffusion 3.Combination of Dissolution & Diffusion 4.Osmotic pressure controlled system References
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Digestive System
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Concept Controlled drug delivery is one which
delivers the drug at a predetermined rate, for locally or systemically, for a specified period of time.
Continuous oral delivery of drugs at predictable & reproducible kinetics for predetermined period throughout the course of GIT.
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Plasma concentration time profile
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Challenges in Oral Drug Delivery
Development of drug delivery system Delivering a drug at therapeutically effective rate to desirable site.
Modulation of GI transit time Transportation of drug to target site.
Minimization of first pass elimination
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Advantages
Total dose is low.
Reduced GI side effects.
Reduced dosing frequency.
Better patient acceptance and compliance.
Less fluctuation at plasma drug levels.
More uniform drug effect
Improved efficacy/safety ratio.
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Disadvantages
Dose dumping.
Reduced potential for accurate dose adjustment.
Need of additional patient education.
Stability problem.
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Mechanism aspects of Oral drug delivery formulation
1.Dissolution : 1.Matrix 2.Encapsulation
2.Diffusion : 1.Matrix 2.Reservoir
3.Combination of both dissolution & diffusion.
4.Osmotic pressure controlled system
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Dissolution Definition:
Solid substances solubilizes in a given solvent.
Mass transfer from solid to liquid.
Rate determining step: Diffusion from solid to liquid.
Several theories to explain dissolution – Diffusion layer theory (imp) Surface renewal theory Limited solvation theory.
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Noyes Whitney Equation
dc/dt = kD.A (Cs – C )dc/dt = D/h A. (Cs – C)
dc/dt = Dissolution rate. k= Dissolution rate constant (1st order). D = Diffusion coefficient/diffusivity Cs = Saturation/ maximum drug solubility. C =Con. Of drug in bulk solution. Cs-C=concentration gradient. h =Thickness of diffusion layer.
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Matrix Type
Also called as Monolith dissolution controlled system.
Controlled dissolution by: 1.Altering porosity of tablet. 2.Decreasing its wettebility. 3.Dissolving at slower rate.
First order drug release.
Drug release determined by dissolution rate of polymer.
Examples: Dimetane extencaps, Dimetapp extentabs.
Soluble drug
Slowly dissolving matrix
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Encapsulation
Called as Coating dissolution controlled system.
Dissolution rate of coat depends upon stability & thickness of coating.
Masks colour,odour,taste,minimising GI irritation.
One of the microencapsulation method is used.
Examples: Ornade spansules,
Chlortrimeton Repetabs
Soluble drug
Slowly dissolving or erodible coat
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Diffusion
Major process for absorption.
No energy required.
Drug molecules diffuse from a region of higher concentration to lower concentration until equilibrium is attainded.
Directly proportional to the concentration gradient across the membrane.
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Matrix Diffusion Types
Rigid Matrix Diffusion Materials used are insoluble plastics such as PVP & fatty acids. Swellable Matrix Diffusion
1. Also called as Glassy hydrogels.Popular for sustaining the release of highly water soluble drugs. 2. Materials used are hydrophilic gums. Examples : Natural- Guar gum,Tragacanth. Semisynthetic -HPMC,CMC,Xanthum gum. Synthetic -Polyacrilamides. Examples: Glucotrol XL, Procardia XL
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Matrix system
Rate controlling step:
Diffusion of dissolved drug in matrix.
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Higuchi Equation
Q = DE/T (2A.E Cs)Cs.t)1/2
Where , Q=amt of drug release per unit surface area at time t. D=diffusion coefficient of drug in the release medium. E=porosity of matrix. Cs=solubility of drug in release medium. T=tortuosity of matrix. A=concentration of drug present in matrix per unit volume.
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Reservoir System
Also called as Laminated matrix device. Hollow system containing an inner core surrounded
in water insoluble membrane. Polymer can be applied by coating or micro
encapsulation. Rate controlling mechanism - partitioning into
membrane with subsequent release into surrounding fluid by diffusion.
Commonly used polymers - HPC, ethyl cellulose & polyvinyl acetate.
Examples: Nico-400, Nitro-Bid
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Reservoir System Rate controlling
steps : Polymeric content in
coating, thickness of coating, hardness of microcapsule.
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Dissolution & Diffusion Controlled Release system
Drug encased in a partially soluble membrane.
Pores are created due to dissolution of parts of membrane.
It permits entry of aqueous medium into core & drug dissolution.
Diffusion of dissolved drug out of system.
Ex- Ethyl cellulose & PVP mixture dissolves in water & create pores of insoluble ethyl cellulose membrane.
Insoluble membrane
Pore created by dissolution of soluble fraction of membrane
Entry of dissolution fluid
Drug diffusion
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Osmotic Pressure Controlled Drug Delivery System
Definition
Procedure
Diagram
Modifications
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Osmosis - Movement of solvent from lower to higher concentration. - The passage of solvent into a solution through
semipermeable membrane.
Semipermeable Membrane Molecules are permitted only to one component (Water).
Osmotic pressureIt is the hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane due to difference in concentration of solutes.
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Osmotic Pressure Controlled System
Provides zero order release
Drug may be osmotically active, or combined with an osmotically active salt (e.g., NaCl).
Semipermeable membrane usually made from cellulose acetate.
More suitable for hydrophilic drug.
Examples: Glucotrol XL, Procardia XL,
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Equation
(Q/t) z = Pw Am/ hm (πs-πe )
(Q/t)= Rate of zero order drug release.
Pw, Am & hm= water permeability, effective surface area & thickness of semipermeable membrane.
πs= osmotic pressure of saturated solution of osmotically active drug or salt in system.
πe = osmotic pressure of GI fluid.
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Osmotic Pressure Controlled System
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Osmotic Pressure Controlled System
Modifications
- Immediate release system.- Osmotically active compartment system
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Immediate Release System
Activation of system is done. Dividing a dose into two parts. One third immediate release. Two third controlled release. Encapsulated into semipermeable
membrane. e.g. : Phenyl propanolamine.
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Osmotically active system
Two compartments separated by movable partition.
Osmotically active compartment absorbs water from GIT.
Creates osmotic pressure.
Partition moves upward & then drug releases.
Ex: Nifedipine.
Movable partition
Delivery orifice
Osmotically active compartment
Drug compartment
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Some Popular Brand names used for OCDDS
Spansule capsule ( SK & F ) Sequal capsule (Lederle ) Extentab tablets ( Robins ) Timespan tablet ( Roche ) Dospan tablet ( Merrell Dow ) Chronotab tablet ( Schering ) Plateau capsule ( Marion ) Tempule capsule ( Armour )
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Some Examples of OCDDS Propranolol (Inderal LA) Methyiphenidate HCl (RitalinSR) Iron (Slow-Fe) GITS-Prazosin (Minipress) Morphine sulfate (Roxanol SR) Decongestant & antihistamine (Resaid SR, Novafed SR
Dristan) Pseudoephedrine HCI (Sudafed SA) Potassium (Micro-K, Slow-K, Klotrix) Antitussive combinations (Rescap, Ornade Spansules) Chlorpheniramine maleate (ChlorTrimeton) Decongestant, antihistamine and anticholinergic (Dallergy,
Supres)
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Recent Trends : Extended release formulation of Bupropion
Bupropion is used in the treatment of major depressive disorder.
Conventional formulation has to be administered 3 times daily
Initially 150 mg ER formulation was introduced for bid regimen
Later on 300 mg ER formulation was introduced for once daily regimen
For ER formulation provide similar Cmax and AUC values as compared to immediate release formulation at steady state.
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Recent Trends : Extended release formulation of Bupropion
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Recent Trends: OROS Technology (ALZA corporation)
Single layer tablet: Drug core (water soluble drug with or without excipients) Semipermeable membrane with a drilled orifice Water imbibition by the core because of osmotic action results in drug dissolution, which is released at a controlled rate through the orifice Not suitable for water insoluble drugs. Examples: Sudafed 24 hours (Pseudoephedrine); Volmax
(Salbutamol)
ELEMENTARY OSMOTIC PUMP
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Recent trends: Geomatrix® (SKY Parma)
This technology Controls amount, timing and location of release in body.
-Formulation with predictable and reproducible drug release profile.-Controls rate of drug diffusion throughout release process, ensuring 100% release Products
Products in market:Cordicant -uno®Madopar DRSULAR ER
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References
Novel drug delivery system , volume 50, Y.W.Chien
The theory & practice of industrial pharmacy, Leon Lachman , Herbert A.Lieberman, Joseph L.Kanig,3 rd edition.
The Eastern pharmacist, november 1993. Sustained release drugs, V R.Gudsoorkar & D.Rambhau page 27-32
Biopharmaceuitics & pharmacokinetics, D M.Brahmankar & Sunil B. Jaiswal.
www.google.com
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