Copolymers polylactic acids

Poly(b-hydroxybutyric acid), PHBA 3-hydroxy butyrate-valerate copolymer Polylactic acid, PLA, polyglycolides, polybutyric acid or copolymers of butyric and valeric acid... 

Similar to pure polyglycoHc acid and pure polylactic acid, the 90 10 glycolide lactide copolymer is also weakened by gamma irradiation. The normal in vivo absorption time of about 70 days for fibrous material can be decreased to less than about 28 days by simple exposure to gamma radiation in excess of 50 kGy (5 Mrads) (35). 

FIGURE 5 Stepwise synthesis of a triblock copolymer (PCL-PLA-PCL) of PCL and polylactic acid using aluminum coordination catalysts to minimize randomization of the block structure by transesterification. (From Ref. 43.)... 

FIGURE 12 Control of the rate of release of methadone from microspheres by the use of blends of a e-caprolactone-lactic acid copolymer and polylactic acid. (From Ref. 63.)... 

CGP 57813 is a peptidomimetic inhibitor of human HIV-1 protease. This lipophilic compound has been successfully entrapped in polylactic acid (PLA) and into pH-sensitive methacrylic acid copolymer particles (EUDRAGIT L 1 GO-55) [69], After the application of a film-coating, the plasma concentration was acceptable and reached similar levels as with injections of drug-loaded PLA carriers. To hinder the proteolytic degradation of a drug, two types of enteric-coated pellets were applied simultaneously. One contained the protease inhibitor coated... 

Chemically-Controlled Systems. In these systems, the polymer matrix contains chemically-labile bonds. On exposure to water or enzymes the bonds hydrolyze, erode the three dimensional structure of the polymer and release the incorporated reagent into the surrounding medium. Depending on the polymer used, the erosion products may act as interferences, such as by altering the pH of the solution. Examples of these systems are polyglycolic acid (PGA) and a polyglycolic acid - polylactic acid (PGA/PLA) copolymer. PGA hydrolyzes to hydroxyacetic acid, and PGA/PLA hydrolyzes to lactic acid and hydroxyacetic acid. Other chemically-controlled systems are based on polyorthoesters, polycaprolactones, polyaminoacids, and polyanhydrides. 

Athanasiou, K. A., Niederauer, G. G., and Agrawal, C. M. (1996), Sterilization, toxicity, biocompatibihty and clinical apphcations of polylactic acid/polyglycolic acid copolymers. Biomaterials, 17, 93-102. 

Ogawa, Y., Yamamoto, M.,Takada, S., and Shimamoto, T. (1988), Controlled release of leuprolide acetate from polylactic acid or copolymer ratio of polymer, Chem. Pharm. Bull, 36,1502-1507. 

Block copolymers, (IV), consisting of succinic acid coupled with propylene glycol and then capped with hexamethylene diisocyanate and reacted with polylactic acid were prepared by Imamura [5] and used as biodegradable containers. 

Amphiphilic block copolymers consisting of polylactic acid or poly(lactic acid-h-glycolic acid) terminated with tocopherol or cholesterol were prepared by Seo [1] and used as drug delivery agents for Paclitaxel . 

Povidone can also be used as a hydrophilic component or pore former in preparations that contain sustained-release auxiliaries like polyvinyl acetate, cellulose derivatives like HPMC [490, 509, 660], alginate [461], cetylacohol [600], polylactic acid [5o6],Gelucire [510],polyvinyl alcohol [522],ceresine wax [523], stearic acid [606] or methacrylate copolymers [491] to control or regulate the release of active substances, as binders and/or sometimes as plasticizers. They can also be extruded together with the active substance in melted stearyl alcohol and filled into hard gelatin capsules to achieve the same effect [471]. Ocular delivery systems are also described [598]. 

From the perspective of biocompatibility, degradability, and process-ability, synthetic polymers have many advantages over complex natural polymers such as collagen. One class of polymers in particular, polyesters in the family of polylactic acid (PLA), polyglycolic acid (PGA), and copolymers of lactic and glycolic acids (PLGAs), most closely meets the listed criteria. These polymers have been approved by the FDA for in vivo... 

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