Bennink H J
Free University, Brussels, Belgium.
Eur J Contracept Reprod Health Care. 2000 Sep;5 Suppl 2:12-20.
This paper reviews pharmacokinetic and pharmacodynamic studies with Implanon, which provides serum etonogestrel levels sufficient to inhibit ovulation within 8 h of insertion. After a peak of 813 pg/ml at 4 days, levels reach steady state (200 pg/ml) after 4-6 months and remain sufficient to prevent ovulation for 3 years. Variability is lower than with Norplant. Etonogestrel levels are similar in most ethnic groups, but 40% higher in women weighing < 50 kg. After implant removal, etonogestrel is not detectable within 1 week. Implanon inhibits ovulation by preventing the mid-cycle luteinizing hormone peak. Although it initially suppresses follicular development and estradiol production, ovarian activity slowly increases after 6 months, and follicle stimulating hormone and estradiol levels are almost normal. Endogenous progesterone levels remain in the subovulatory range for > 3 years in most subjects. In ovarian ultrasound studies, ovulation occurred in < 5% of users after 30 months of use. Ovulation was observed in most women within 3-4 weeks of implant removal. The pharmacokinetics and pharmacodynamics of Implanon indicate that it has high contraceptive efficacy, as reflected in a zero pregnancy rate over 5,629 woman-years of use. Its excellent reliability, ease of use, and reversibility make Implanon a valuable addition to current contraceptives.
本文综述了依托孕烯植入剂的药代动力学和药效学研究，该植入剂在插入后8小时内即可提供足以抑制排卵的血清依托孕烯水平。在4天时达到813 pg/ml的峰值后，血药浓度在4 - 6个月后达到稳态（200 pg/ml），并在3年内保持足以防止排卵的水平。其变异性低于左炔诺孕酮皮下埋植剂。大多数种族群体的依托孕烯水平相似，但体重<50 kg的女性体内的依托孕烯水平要高出40%。取出植入剂后，1周内检测不到依托孕烯。依托孕烯植入剂通过阻止月经周期中期促黄体生成素峰值来抑制排卵。虽然它最初会抑制卵泡发育和雌二醇生成，但6个月后卵巢活性会缓慢增加，促卵泡生成素和雌二醇水平几乎恢复正常。在大多数受试者中，内源性孕酮水平在3年多的时间里一直保持在低于排卵水平的范围内。在卵巢超声研究中，使用30个月后，<5%的使用者发生排卵。在取出植入剂后的3 - 4周内，大多数女性都出现了排卵。依托孕烯植入剂的药代动力学和药效学表明其具有较高的避孕效果，在5629妇女年（人年）的使用期间妊娠率为零，这一点就体现了这一点。其出色的可靠性、易用性和可逆性使依托孕烯植入剂成为现有避孕药具中的一个有价值的补充。
