Current status of NORPLANT subdermal implants for contraception.
This article is a report of recent research on NORPLANT subdermal implants. The system consists of 6 3cm silastic (polydimethylsiloxane) capsules, implanted in the upper arm by a simple surgical procedure, which release the levonorgestrel contraceptive slowly over a period of 5 years. Net cumulative failure rate has been shown to be 1.5% over 5 years. The surgical technics for implantation are described: they can be performed in 10-15 minutes by a physician or trained nurse, with a minimal infection rate. The capsule does not biodegrade and must be removed, a minor operation taking 15-25 minutes. After insertion, blood levels of levonogestrel sufficient to prevent conception are achieved within 24 hours. After 1 year of use the average release rate is 30-35 mcg per day. The hormone release appears in tests to affect cervical mucus and the endometrium, and possibly to suppress ovulation. There is a current attempt to study the latter phenomenon by ultrasound. The 4-year cumulative termination rate was 50.9 + or - 2.8%, menstrual problems being the most important medical reason (14.1% + or - 2.0). There were differences between clinics in reasons for termination. Monitoring of most indicators appears to suggest little in the way of metabolic changes. The use of the implants should not increase the risk of coronary heart disease. Serum levels of levonorgestrel decline rapidly after removal, and 90% of women removing the implant in order to conceive had become pregnant after 2 years. Clinical tests of a more effective and acceptable 2-implant system (NORPLANT-2) are now taking place. The present system has proven to be acceptable in Finland and the US, with over 80% of the participants recommending the method to friends.