The contraceptive efficacy of Implanon: a review of clinical trials and marketing experience.

OBJECTIVES

To evaluate the contraceptive efficacy of the etonogestrel-releasing implant Implanon as assessed in international studies and during nine years of marketing experience.

METHODS

The analysis included 11 international studies and data collected during nine years of marketing experience (1998--2007). Seven of these studies were noncomparative; the four other studies included the 6-rod levonorgestrel implant system or an intrauterine device as a comparator. All studies except one were of at least two years in duration, and all had contraceptive efficacy as the objective. Market data were provided unsolicited to Organon, part of Schering Plough.

RESULTS

The integrated efficacy analysis included 923 non-breastfeeding women who were exposed to the implant for 24,100 cycles. No in-treatment or pretreatment pregnancies were reported. Fifty posttreatment pregnancies were reported, six of which occurred within 14 days of implant removal, indicating that fertility had quickly returned. Over a nine-year marketing period an overall pregnancy rate of 0.049 per 100 implants sold (estimated Pearl Index = 0.031 based on all pregnancies reported) was calculated. When only counting contraceptive method failures the pregnancy rate amounts to 0.010 per 100 implants sold (estimated Pearl Index = 0.006).

CONCLUSION

Implanon is a highly effective and quickly reversible subdermal method of long-acting hormonal contraception for women. Typical use of this implant achieves a contraceptive protection exceeding 99%.