CONTRACEPTIVE EFFICACY, PHARMACOKINETICS, AND SAFETY OF ANNUELLE(R) BIODEGRADABLE NORETHINDRONE PELLET IMPLANTS

Objective: To evaluate the contraceptive efficacy, pharmacokinetics, a nd safety of two formulations of Annuelle (Endocon, inc., South Walpol e, MA) biodegradable norethindrone (NET) SC pellet implants. Design: P rospective observational study. Setting: Two clinical sites in the Uni ted States, Patient(s): Thirty-nine healthy, fertile, sexually active women. Intervention(s): Nineteen women received a four-pellet system c ontaining 174 mg NET; 20 women received a five-pellet system containin g 266.5 mg NET. Main Outcome Measure(s): Contraceptive efficacy, media n serum NET levels, adverse events. Result(s): No pregnancies were obs erved in 293 woman-months in the four-pellet group or in 375 woman-mon ths in the five-pellet group. An initial burst in median serum NET lev els occurred in the first 24 hours postinsertion followed by a steady decline over the next 3 years. Norethindrone levels varied considerabl y among women. The main side effect was bleeding abnormalities, which persisted in half the participants for up to 2 years. No serious adver se events were reported that were related to the pellets. Pellet inser tion and removal generally were uncomplicated. Conclusion(s): Annuelle shows potential as an effective, safe contraceptive with distinct adv antages over other long-acting agents, because it is biodegradable but can be removed if problems arise or if fertility is desired.