Injectable Contraceptives and Contraceptive Vaginal Rings

Abstract

This chapter in a book on contraception reviews injectable contraceptive steroids and contraceptive vaginal rings. The 3 types of injectables currently used by 5 million women worldwide are presented with an emphasis on depo-medroxyprogesterone acetate (DMPA), its effectiveness, formulation and serum levels, method of action, associated menstrual bleeding patterns, metabolic effects, risks, and benefits. Norethindrone enanthate (NET-EN) is discussed next, along with its side effects and associated bleeding patterns. Finally, progesterone-estrogen injectables are considered. The illustrations which accompany the discussion of injectables show 1) serum medroxyprogesterone acetate, estradiol, and progesterone concentrations in 3 women after intramuscular injection of 150 mg of DMPA; 2) the percentage of women with bleeding/spotting at various times during a 30-day cycle while receiving injections of 150 mg DMPA every 3 months; 3) risks of various cancers associated with DMPA use; 4) serum levels of luteinizing hormone, follicle-stimulating hormone, progesterone, estradiol, and norethindrone before and 4 months after a single injection of 200 mg NET-EN; and 5) net termination rates per 100 women in a comparative study of DMPA and NET-EN. The design and development of contraceptive vaginal rings (CVRs) is discussed next, followed by a description of the progestin-only CVRs designed for discontinuous use (containing medroxyprogesterone acetate, norethindrone, or norgestrel) and those designed for continuous use (containing levonorgestrel, progesterone, megestrol, and 3 keto-desogestrel). The third type of CVR considered contains estrogen and progestin and is meant for intermittent use. The varieties available are levonorgestrel or norethindrone in combination with estradiol and ST-1435, 3-keto-desogestrel, or norethindrone acetate in combination with ethinyl estradiol. The major problems with CVRs are vaginal infections, cervical changes, spontaneous expulsion, and other vaginally-related problems. After reviewing the data on acceptability, the author concludes that CVRs provide advantages over oral contraceptives and should achieve widespread use after further study and development.