In vivo characteristics of low‐molecular‐weight copoly(L‐lactic acid/DL‐hydroxyisocaproic acid) with parabolic‐type and S‐type degradation pattersn

Abstract

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.

Drug release mechanisms from bioerodible polymers for stent application

“…In any case, the exponential decrease of the average molecular weight with apparent first-order degradation (without the appearance of bimodality) indicated a random chain scission and a negligible effect of autocatalysis. Similar studies on the effect of composition on degradation had also been reported by Wang and Wu [5]. In a study [5] recorded.…”

“…Similar studies on the effect of composition on degradation had also been reported by Wang and Wu [5]. In a study [5] recorded. It might be noted that it was quite difficult to measure the percent water uptake for samples after the day.…”

“…Sampath et al [37] investigated PlLA microcapsules and cylindrical implants as localized antibiotic therapy. The release of gentamicin sulfate was strongly dependent on the loading (5,10,33, 50, 67 % w/w). The release profiles of microcapsules containing 50 and 67 % w/w gentacymin are similar to that of microcapsules containing 33 % w/w drug, while microcapsules with 20 % w/w drug had a release profile similar to those with 10 % w/w loading and complete drug release occurred within 3 weeks.…”

“…Generally, such polymers that lose its weight over time in the living body are called absorbable, resorbable or bioabsorbable polymer as well as biodegradable polymer, regardless of its degradation mode; enzymatic as well as non-enzymatic hydrolysis [4]. For biodegradable products to be useful, the break-down products must be non-toxic; also, the body must have a mechanism for eliminating the by products [5]. Homopolymers and copolymers based on L-lactic acid, D, L-lactic acid and glycolic acid have received interest in their medical and pharmaceutical field because of their biodegardability and toxicological safety.…”

“…The films subsequently were air-and vacuum-dried to obtain the initial samples. The thin (5)(6)(7)(8)(9)(10) PLGA 75:25 films were of 60 = 62 kDa (PI=14.8), and the thick PLGA 75:25 films (85-100 were of = 58 kDa (PI=6.4). After processing, the thin PLGA 50:50 films were of = 37 kDa (PI=8.9), and the thick PLGA 50:50 samples were of = 34 kDa (PI=4.5).…”