Contraceptive action of megestrol acetate implants in women

Silastic capsules containing megestrol acetate were implanted under the skin for evaluation as a long-term contraceptive method in women. Inhibition of fertility lasting from 9 to 12 months was obtained after a single implantation of 4 capsules. During this period the pregnancy rate was 9.4 and 6.0 per 100 women-years respectively with 2 types of capsules. Restoration of fertility took place promptly after removal of the implant. Spotting or breakthrough bleeding occurred in 30% of the cycles at the beginning of treatment but decreased gradually thereafter to a rate of 8%. This figure did not increase after replacing the capsules with a new set. The only major complication associated with this treatment was a higher than normal incidence of ectopic pregnancies. It is concluded that these implants at the doses tested in this study can reduce fertility for periods up to 1 year but their acceptability as a contraceptive method in humans is limited mainly by their low effectiveness and the increased medical risk associated with method failures.