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Parenteral Controlled Release Drug Delivery Systems (IMPLANTABLE DRUG DELIVERY) :

Parenteral Controlled Release Drug Delivery Systems (IMPLANTABLE DRUG DELIVERY) Presented By: Naga Sravan Kumar Varma V 1 st M. Pharm. Dept. of Pharmaceutics JSSCP, Mysore. Presented to: D r. Hemant Kumar Yadav Dept. of Pharmaceutics JSSCP, Mysore.


Introduction Implants are typically placed subcutaneously to sustain drug release T he General Mechanism Involved : Drug diffusion Polymer dissolution A combination of both

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First generation of implantable drug delivery systems was produced by compressing drug crystals, with or without a small fraction of pharmaceutical excipients , into tiny, cylindrical solid pellets that could be readily implanted into subcutaneous tissue by means of a Kearns pellet injector or by making a small skin incision.

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Subcutaneous tissue is rich in fat but poor in hemoperfusion and nerves. Because of its ready access to implantation, slow drug absorption, and low reactivity to the insertion of foreign materials, it has become a route of choice for prolonged drug administration.

Various approaches of implantable drug delivery are: :

Various approaches of implantable drug delivery are: Controlled drug delivery by diffusion process Membrane permeation-controlled drug delivery using Nonporous membranes Microporous membranes Semipermeable membranes Matrix diffusion-controlled drug delivery using Lipophilic polymers Hydrophilic polymers Porous polymers

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Microreservoir Dissolution controlled drug delivery using Hydrophilic reservoir in lipophilic matrix Lipophilic reservoir in hydrophilic matrix Controlled drug delivery by activation process Osmotic pressure activated drug delivery Vapor pressure activated drug delivery Magnetically activated drug delivery Phonophoresis activated drug delivery Hydration activated drug delivery Hydrolysis activated drug delivery

Controlled Drug Release by Diffusion:

Controlled Drug Release by Diffusion 1. Membrane Permeation Controlled Drug Delivery: In this implantable controlled-release drug delivery device the drug reservoir is encapsulated within a capsule shaped or spherical compartment that is totally enclosed by a rate-controlling polymer membrane. The drug reservoir can be either drug solid particles or a dispersion of drug solid particles in a liquid or a solid dispersing medium. The polymeric membrane can be fabricated from a homogenous or heterogenous nonporous polymeric material or a microporous membrane.

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The encapsulation of drug reservoir inside the polymeric membrane can be accomplished by encapsulation, microencapsulation, extrusion, molding, or other techniques. K m/r D m h d + K a/m D d h m Q/t = K m/r K a/m D d D m C R K m/r and K a/m are the partition coefficients for the interfacial partitioning of drug molecules From the reservoir to the rate controlling membrane and the membrane to the surrounding aqueous diffusion layer. D m and D d are diffusion coefficient in the rate controlling membrane with thickness hm and in aqueous diffusion layer with thickness hd

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Examples: Norplant, Ocusert System

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2. Matrix Diffusion-controlled drug delivery devices: In this implantable controlled-release drug delivery device the drug reservoir is formed by homogeneous dispersion of drug solid particles throughout a lipophilic or hydrophilic polymer matrix. The dispersion of drug solid particles in the polymer matrix can be accomplished by blending drug solids with a viscous liquid polymer or a semisolid polymer at room temperature followed by cross-linking of polymer chains or by mixing drug solids with a melted polymer at an elevated temperature.

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These drug-polymer dispersions are then molded or extruded to form a drug delivery device of various shapes and sizes. Drug release is time dependent Q/t ½ = (2AC R Dp) 1/2 A is initial drug loading dose in the polymer matrix C R drug solubility in polymer Dp diffusivity of the drug molecules Eg : Compudose implant which contains estradiol

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3. Microreservoir Dissolution controlled drug delivery: In this system the drug reservoir, which is a suspension of drug crystals in an aqueous solution of a water-miscible polymer, forms a homogenous dispersion , unleachable , microscopic drug reservoirs in a polymer matrix. Depending on the physico -chemical properties of the drugs and the desired rate of drug release, the device can be further coated with a layer of biocompatible polymer to modify the mechanism and the rate of drug release.

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Eg : Syncro -Mate-C Implant


Reference Joseph R. Robinson, Vincent H. L. Lee; Controlled Drug Delivery Fundamentals and Applications; Second Edition; Page No.: 482-497 Novel drug delivery system, by Yie.W.Chien page no -: 311-407

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