Efficacy, Safety, and Acceptability of Acidform (Amphora) and Nonoxynol-9 Contraceptive Vaginal Gels [16N]

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Most contraceptive vaginal gels are surfactant-based spermicides that contain the active ingredient nonoxynol-9, which kills sperm by destroying the cell membrane. Acidform gel (Amphora™), a new contraceptive vaginal gel, works by buffering the vaginal pH so that it maintains the vaginal environment at an acid pH despite the alkalinity of the incoming semen.


A multicenter, randomized, open-label trial was conducted in 49 sites in the US and 13 sites in Russia to assess the 6-month pregnancy percentage of Acidform gel compared to nonoxynol-9. Participants were healthy, sexually active women between 18 and 45 years old. The primary outcome was pregnancy percentage over 6 months; secondary outcomes included acceptability and safety.


A total of 1,665 women were randomized to Acidform and 1,659 to nonoxynol-9. In the typical-use population (ages 18 to 35) the 6-month pregnancy percentages were 10.5% (95% CI 8.6–12.3) for Acidform and 10.0% (95% CI 8.1–11.9) for nonoxynol-9. With perfect use, the 6-month pregnancy percentage was 4.1% (95% CI 2.7–5.4) with Acidform. This was nearly identical to the 6-month percentage of 4.2% (95% CI 2.8–5.6) with nonoxynol-9. Fewer than 2% of subjects had adverse events that led to discontinuation. Significantly more Acidform users liked the method and would use it again (P less than .05 for both comparisons).


Acidform gel demonstrated 96% contraceptive efficacy at 6 months with perfect use. Both products studied were acceptable and few subjects had adverse events; however, more women using Acidform gel liked the method and would use it again.

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