Contraceptive effectiveness and safety of five nonoxynol-9 spermicides: A randomized trial

OBJECTIVES: To estimate and compare the effectiveness and safety of 5 spermicides over 6 and 7 months of use, respectively. The spermicides included 3 gels containing 52.5 mg, 100 mg, and 150 mg of nonoxynol-9 per dose and a film and a suppository, each containing 100 mg of nonoxynol-9 per dose. METHODS: Women wishing to use only spermicide for contraception for 7 months were randomly assigned to use I of the 5 spermicides with emergency contraception backup. Participants were followed up for up to 30 weeks after admission. RESULTS: Of 1,536 women enrolled, 868 (57%) either relied on the spermicide for 6 months or became pregnant. The probability of pregnancy during 6 months of typical use of the spermicide was 22% (95% confidence limits 16%, 28%) in the 52.5-mg gel group, 16% (10%,21%) in the 100-mg gel group, 14% (9%, 19%) in the 150-mg gel group, 12% (7%, 17%) in the film group, and 10% (6%,15%) in the suppository group. The pregnancy risk in the 52.5-mg gel group was significantly different (P < .05) from that in either of the other gel groups. The pregnancy risks in the three 100-mg product groups were not significantly different (P = .35). No significant differences among groups were found in the 7-month probability of specified urogenital conditions. CONCLUSION: The gel with the lowest amount of nonoxynol-9 was less effective than the 2 higher-dose gels. Among 3 products containing 100 mg of nonoxynol-9, formulation did not significantly affect pregnancy risk. All products were safe. (C) 2004 by The American College of Obstetricians and Gynecologists.