Contraception with long-acting subdermal implants. A five-year clinical trial with Silastic covered rod implants containing levonorgestrel. The International Committee for Contraception Research (ICCR) of the Population Council.

A total of 189 women volunteered to accept subdermal implants for contraception. The implants were "covered rods", consisting of a core rod containing equal parts by weight of levonorgestrel and polydimethylsiloxane and sealed inside a thin-walled tube of Silastic tubing with medical adhesive. In one study 78 women used 4 3cm rods (study 07) and in the other 111 women used 6 3cm rods. In 5 years of use there were no pregnancies in either group. Terminations because of menstrual problems were twice as frequent among the 4-rod users than among users of the 6 rods. Menstrual pattern analysis is presented for the two rod regimens and compared with the previously reported patterns for the 6-capsule regimen (NORPLANT). Long--term in vivo release rates are also presented.