Clinical experience with implant contraception.

Subdermal implants of polysiloxane (Silastic) capsules containing a number of synthetic progestagens have been studied in clinical trials to determine their contraceptive effectiveness and acceptability. The steroids studied include norgestrienone (R2010), gestrigone (R2323), megestrol acetate, d-norgestrel, norethindrone, ST-1435, lynestrenol and R-1364. With some of these steroids, studies have been undertaken with a varying number of implanted capsules. The estimated duration of use varies from 6 months to 6 years depending on dose and release rate of the individual steroid. The results of these studies involving about 5000 women in 8 years, indicate in general a high rate of effectiveness, as well as acceptability. Continuation rates at one year were generally 80% or greater. Abnormal bleeding patterns are the major disadvantage. Studies with implatns containing a combination of estrogen and progestogen are being undertaken in an attempt to improve the bleeding pattern.