Contraceptive Implants 皮下埋植避孕剂

The Norplant® implant system was a progestin-based contraception medication formulated for five years of continuous use. The implant system consisted of six soft silastic implants, each containing 36 mg of levonorgestrel. The implants were 34 mm long and 2.4 mm in diameter. They were placed in a fan-shaped arrangement into the subcutaneous tissue on the medical aspect of a woman’s nondominant upper arm. It was removed from the US market in July 2002. A second generation, Norplant II® (also known as Jadelle®), consists of two small (43 mm X 2.5 mm) silicone rods, each containing 75 mg of levonorgestrel, instead of the original six capsules.

Norplant®是孕激素埋植剂，持续有效时间为五年。Norplant含有六个软硅胶植入器，每个植入器内含有36mg左炔诺孕酮。植入器长34mm，直径2.4mm，以扇形排列植入放进女性非惯用手臂内侧皮下。2002年7月后美国市场上不再使用这种类型的埋植剂。第二代Norplant II®(也称为Jadelle®)改进了原来配置，把六个软硅胶植入器改为两个小的硅胶棒(43mm X 2.5mm)，每个硅胶棒含有75mg左炔诺孕酮。

The current contraceptive implant system available in the United States consists of a single rod (4 cm in length and 2 mm in diameter) of ethylene vinyl acetate copolymer core containing 68 mg of etonogestrel. The device allows for controlled release of etonogestrel over a period of three years. Etonogestrel is the active metabolite of desogestrel. It does not contain latex, is not biodegradable, and originally was not radiopaque. It was originally marketed as Implanon®. The insertion device was redesigned and the implant device made radiopaque and renamed Nexplanon®. Implanon was phased out in December 2012; since that day only Nexplanon has been available. The contraceptive implant is the most effective method of reversible contraception, with a typical-use pregnancy rate of 0.05% (1).

目前美国可用的皮下埋植剂由一根乙烯醋酸乙烯酯共聚物芯棒(长4cm，直径2mm)组成，内含68mg依托孕烯，会在三年内有控制性地释放依托孕烯。依托孕烯是去氧孕烯的活性代谢物。这种皮下埋植剂上市的名字是Impanon®，不含乳胶，不可生物降解，最初设计是不透辐射的。后来植入器经过重新设计改为可透辐射的，产品更名为Nexplanon®。Impanon于2012年12月退出市场，目前只有Nexplanon在售。皮下埋植避孕器是最有效的可逆避孕方法，理论使用妊娠率为0.05%(1)。

The most common side effects are changes in menstrual bleeding pattern including amenorrhea, oligomenorrhea, or prolonged bleeding. The bleeding pattern with contraceptive implant use is unpredictable and is cited as the most common reason for device discontinuation. However, a significant noncontraceptive benefit is a decrease in dysmenorrhea. Other reported adverse effects include gastrointestinal difficulties, headaches, acne, breast pain, vaginitis, and weight gain. According to the package insert, weight gain was reported in only 2.3% of patients who chose to discontinue the implant.

使用皮下埋植避孕药最常见的副作用是月经紊乱，包括闭经，月经稀发或出血时间延长。使用期间月经出血情况无法预测，这是患者停止继续使用埋植剂的最常见原因。不过，使有埋植剂除了避孕的作用外还有一个很明显的好处，能减少痛经的发生率。其他报告的不良反应包括胃肠道不适，头痛，痤疮，乳房疼痛，阴道炎和体重增加。根据包装说明书，只有2.3%选择停止使用埋植剂的患者有体重增加的情况。

The contraceptive implant is safe to insert anytime in nonbreastfeeding women after childbirth. In breastfeeding women, it is optimal to wait four weeks after childbirth because of theoretic concerns regarding milk production and infant growth and development. A randomized trial compared postpartum insertion of the etonogestrel contraceptive impant at one to three days with standard insertion at four to eight weeks postpartum. No differences were found in breastfeeding outcomes between the groups, including lactogenesis and the risk of lactation failure. An additional nonrandomized comparative study compared milk composition in 80 women using nonhormonal IUD contraception with the etonogestrel implant. Breast milk composition (measured by total protein, fat, and lactose content) did not differ between the groups, nor did the quantity of breast milk. A three-year follow-up also showed no difference in neonatal body length, biparietal head circumference, and body weight. Given the excellent data regarding efficacy and safety for the contraceptive implant, expanded usage could substantially decrease the unintended pregnancy rate.

埋植避孕剂可以在女性分娩后非母乳喂养期植入。对于正在母乳喂养的女性，理论上出于对泌乳和婴儿生长发育的考虑，最好在分娩四周后再植入。根据一项对产后1至3天植入依托孕烯避孕剂和产后4-8周植入避孕剂的标准做法的随机试验，两组之间的母乳喂养结果没有差异，包括泌乳量和泌乳失败风险。另一项非随机研究对比了80名使用非激素类宫内节育器和依托孕烯植入器后的母乳成分，发现两组之间没有差异(比较总蛋白质，脂肪和乳糖含量)，母乳量也没有差异。三年随访结果也说明新生儿的体长，头部双顶径和体重没有差异。鉴于埋植避孕剂有效性高，安全性佳，扩大使用范围可以大大降低意外妊娠率。

References

参考文献

1. Basinski CM, A review of clinical data for currently approved hysteroscopic sterilization procedures. Rev Obstet Gynecol 2010;3:101-10. (Level III)