An amorphous copolyester of c l a g c acid (LA) and Dbhydroxyisocaproic acid (HICA) with a number-average molecular weight (MJ of 1 600-4800 was synthesized by direct copolycondensation in the absence of catalysts, in order to develop a biodegradable carrier for drug delivery systems. The in vivo degradation pattern was changed into an S-type from a parabolic-type with an increase in molecular weight of copolyester. A luteinizing hormone-releasing hormone agonist, ~~S -G~~'~-[ D -L~U~-L H -R H ethylamide, was incorporated into a fine cychdrical copolyester formulation by the so-called melt-pressing technique m e n the S-type degradable and releasable copoly(LH/HICA) (70/30 mol-Yo) formulations with Mn = 2200 were implanted subcutaneously in the back of rats, the most reasonable serum drug level was observed during the first 15 weeks period, keeping constant at approximately 3 3 ng/ml.
Sequential polydepsipeptides containing both peptide and ester bonds, poly[(L-alanyl)n-gamma-ethyl L-glutamyl-L-lactyl] (n = 0, 1, 2, and 3) (poly[(Ala)n-Glu(OEt)-Lac]), were prepared for application as biodegradable carriers for drug delivery systems. The in vivo degradation of these polymers was evaluated by subcutaneous implantation in the backs of male rats, and was strongly influenced by the number (n) of Ala units in poly[(Ala)n-Glu(OEt)-Lac]. The resulting poly(Ala-Ala-Glu(OEt)-Lac) gave the highest degradability, in which 100% degradation was observed 24 weeks from the start of implantation. A luteinizing-hormone-releasing hormone agonist des-Gly10-[D-Leu6]-LH-RH ethylamide (LH-RH agonist), was incorporated into a sequential poly(Ala-Ala-Glu(OEt)-Lac) carrier by the melt-pressing technique, which gave fine cylindrical polymer formulations with different structures of drug dispersion, e.g., blend-type and sandwich-type formulations. The rate of in vivo release of LH-RH agonist from a blend-type formulation showed a linear decrease with time until its release was finished after 6 weeks' implantation. In contrast, in a sandwich-type formulation, the in vivo release rate was apparently maintained constant over a period of 16 weeks (24 +/- 14 micrograms/day).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.