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生物降解聚合物被用于避孕药物的释放系统,近十多年来已被人们重视,它的优点是当引入人体后随着药物的恒速释放,载体自行降解,无需手术取出。恒定释放甾体药物,避免了口服时血药浓度的波动现象,从而减少了妇女的不规则出血,较易被使用者接受。Beck 等研究了生物降解的聚乳酸(PL-A)作为载体制成的炔诺酮微球注射剂。经第Ⅰ期临床验证,一次注射有效期达6个月。如果甾体药物单纯靠扩散作用释放,PLA 作为载体的应用就会受到一定的限制,因PLA 为玻璃样物,甾体药物很难渗透而扩散,例如孕甾酮在硅橡胶中的渗透性是2.6×10~(-9)g/cm~3/sec,而在PLA 中仅0.000033×10~(-9)g/cm~3/sec。但是具有较大比表面积的含甾体药物的微球制剂,能够补偿药物渗透扩散较慢的现象。
Biodegradable polymers have been used in the delivery system of contraceptives for more than a decade. The advantage of biodegradable polymers is that when the drug is introduced into the human body at a constant rate, the carrier degrades without any surgical removal. Constant release of steroidal drugs, to avoid fluctuations in plasma concentrations of oral orally, thus reducing the irregular bleeding of women, more easily accepted by the user. Beck et al. Studied the preparation of norethindrone microspheres injections using biodegradable polylactic acid (PL-A) as a carrier. After the first phase of clinical validation, an injection of valid for 6 months. If steroid drugs are simply released by diffusion, the application of PLA as a carrier will be limited because PLA is a glass-like substance and steroid drugs hardly permeate and spread, for example, the permeability of progesterone in silicone rubber is 2.6 × 10 ~ (-9) g / cm ~ 3 / sec and only 0.000033 × 10 ~ (-9) g / cm ~ 3 / sec in PLA. However, the steroid-containing microspheres with larger specific surface area can compensate for the slow penetration of drugs.