Vaginal Contraceptives: A time for reappraisal?
Literature on vaginal chemical contraceptive agents is reviewed. Vaginal contraceptives have been in use for more than 2 centuries, and homemade spermicides are still used among some populations. There are basically 4 types of vaginal chemical contraceptives: 1) creams, jellies, and pastes which are squeezed from a tube, 2) suppositories which dissolve in the vagina, 3) aerosol or tablet foams, and 4) water-soluble plastic film (C-film) containing a spermicide. The spermicidal actions of vaginal chemical contraceptives are various. Surface active agents are thought to attach to sperm, thereby inhibiting oxygen uptake and fructolysis. Bactericidal agents, such as phenyl mercuric acetate, quinine compounds, quartenary compounds, and ricinoleic acid and its compounds, act by combining with sulphur and hydrogen bonds in spermatozoa, thus interfering with their metabolism. Surface and bactericidal agents often act synergistically. Highly acidic agents include lactic acid, boric acid, tartaric and citric acids, and gum acacia. FDA standards for the safety and effectiveness of over-the-counter (OTC) drugs are presented. In vitro studies are the 1st phase in testing the effectiveness of a spermicide. The IPPF tests approves spermicidal preparations if 1 ml of a 1:11 solution immobilizes all sperm in .2 ml of semen within 40 seconds after mixing. However, it is questionable whether in vitro tests assure clinical effectiveness. In an in vivo study, only Delfen cream and Emko foam provided full protection after a second insemination. The effectiveness of spermicides in clinical tests is highly variable. Pregnancy rates per 100 woman-years of use as low as 1.75 and as high as 38.3 have been reported. Pregnancy rates for C-film reportedly range from 5.3 to 62 per 100 woman-years of use. The IPPF has estimated that 1,041,500,000 doses of spermicides were distributed in 1971. 1.5-4 million women in the U.S. are estimated to use vaginal foams. However, the introduction of oral contraceptives and the IUD has substantially reduced the number of users of spermicides. The promotion and sale, costs, USAID shipments, and distribution of spermicides are reviewed. Preliminary studies of the in vitro inhibition of N. gonorrhea growth by vaginal chemical contraceptives have been promising.