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应用单纯孕激素避孕的研究已近20年,最常使用的为肌注剂如醋酸甲孕酮(DMPA)及炔诺酮庚酸酯(NET-EN)。为了避免注射剂所见到的很高的初始血药浓度,发展了新的药物释放系统如皮下埋植剂Norplant~R(6支胶囊)及Norplant Ⅱ(2支棒)。Norplant为非生物降解的埋植剂,因所含左旋18甲基炔诺酮(LNG)对硅橡胶的穿透力小,故需要较大的表面积以释放足够的药物从而达到避孕有效浓度,并维持3～5年。另一种含3-酮地索高诺酮(单支)的非生物降解皮下埋植剂也正在研究中,有效期为1年。Capronor为可生物降解的避孕系统,由于其LNG释放率10倍于硅橡胶,所需表面积就少。埋植剂的外层暴露在组织液中一定时间后即分解成为6-羟乙酸,最终成为CO_2与水,因而使用超过有效期后不必手术取出。现对
Progestogen-only contraception has been used for almost 20 years, with intramuscular injections of medroxyprogesterone acetate (DMPA) and norethindrone acetate (NET-EN) most commonly used. In order to avoid the high initial plasma concentration seen in injectables, new drug delivery systems such as Norplant R (6 capsules) and Norplant II (2 rods) have been developed. Norplant is a non-biodegradable implants that require a large surface area to release enough drug to achieve a contraceptive effective concentration due to the low penetration of L-18 norgestrel into the silicone rubber. Maintain 3 to 5 years. Another non-biodegradable subcutaneous implants containing 3-keto cableotene (single) is also under study and is valid for 1 year. Capronor is a biodegradable contraceptive system that requires less surface area due to its LNG release rate of 10 times that of silicone rubber. Implants exposed to the outer layer of tissue fluid after a certain period of time that is decomposed into 6-hydroxyacetic acid, and eventually become CO2 and water, and therefore beyond the validity of the use of surgery without removal. Right now