Objective
To compare contraceptive efficacy, safety, and acceptability of C31G and nonoxynol-9 spermicidal gels.
Methods
We conducted a multicenter, randomized, double-masked, controlled trial to assess whether a gel containing the spermicide C31G was non-inferior to a commercially available product containing nonoxynol-9. Participants were healthy, sexually active females ages 18–40 years. Measured outcomes included pregnancy rates, continuation rates, adverse events, and acceptability. Sample size was calculated at a 2.5% significance level using a one-sided test, based on assumed 6-month pregnancy probability of 15% in the Conceptrol group. Sample size was sufficient to reject, with 80% power, the null hypothesis that pregnancy probability in the C31G arm would be more than 5% higher.
Results
Nine-hundred thirty-two women were randomized in the C31G group and 633 in the nonoxynol-9 group. For randomized subjects with at least one episode of coitus (modified intent-to-treat group), six-month pregnancy probabilities were 12.0% (95% confidence interval (CI) 9.3–14.7%) and 12.0% (95%CI 8.7–15.3%) for C31G and nonoxynol-9 respectively. Twelve-month pregnancy probabilities were 13.8% (95%CI 7.6–20%) for C31G and 19.8% (95%CI 10.9–28.7%) for nonoxynol-9. Two serious adverse events were deemed possibly related to study product, and neither occurred the C31G group. Three-fourths of users in either group reported that they liked their assigned study product. Approximately 40% of subjects discontinued prematurely for reasons other than pregnancy, with 11% lost to follow-up.
Conclusion
C31G demonstrated noninferior contraceptive efficacy compared to nonoxynol-9. Both products were safe and acceptable. C31G may provide another marketable option for women seeking spermicidal contraception.