●●●●● ●●●● ●●0 ●●● ●●●● Controlling drug diffusion rates from dosage forms. Chemically reacting or interacting between the drug substance or its pharmaceutical ba ● arrier and site specific biologic fluids
- Controlling drug diffusion rates from dosage forms. - Chemically reacting or interacting between the drug substance or its pharmaceutical barrier and sitespecific biologic fluids
table 8 10 Depot forms employing polymeric films and matrices Materialss Diagrammatic representation Mechanisms Barrier coating Beeswax, glyceryl monostearate, ethylcellulose, Diffusion nylon(Ultramid IC), acrylic resins (Eudragit retard) 2 Fat embedment Glycerol palmitostearate(Precirol), beeswax, glycowax drug Erosion, hydrolysis of castorwax, aluminium monostearate, carnauba fat, dissolution wax, glyceryl monostearate, stearyl alcohol 3 Plastic matrix Polyethylene Leaching, diffusion Poly(vinyl acetate) drug Polymethacrylate Poly(vinyl chloride) polymer Ethylcellulose 4 Repeat action Cellulose acetylphthalate Dissolution of enteric enterIc 5 Ion exchange Amberlite Dissociation of drug- Dowex resin complex 6 Hydrophilic matrix Carboxymethylcellulose hydrophilic poly Gelation diffusion Sodium carboxymethylcellulose Hydroxypropylmethylcellulose drug 7 Epoxy resin beads Epoxy resins Dissolution of resin or epoxy resin bead swelling, diffusion 8 Microcapsules Polyamides, gelatin or microcapsul 9 Soft gelatin depot Shellac-PEG capsules Poly(vinyl acetate)-PEG Diffusion Materials are not all polymeric. The waxes are included for completeness; these depend on conferring a hydrophobic layer on the drug, tablet, or granule to prevent access of solvent TAfter Ritschel, reference 21
●●●●● ●●●● 1) Coated beads, granules, or ●●●● ●●● ●●●● microspheres In these systems, the drug is distributed onto beads pellets granules, or other particulate systems
1) Coated beads, granules, or microspheres - In these systems, the drug is distributed onto beads, pellets, granules, or other particulate systems