An evaluation of the amount of nonoxynol-9 remaining in the vagina up to 4 h after insertion of a vaginal contraceptive film (VCF) containing 70 mg nonoxynol-9.

ABSTRACT

PIP: The amount of nonoxynol-9 (N-9) remaining in the vagina 0.5, 1.0, 1.5, 2.0, and 4.0 hours after vaginal insertion of a single sheet of a contraceptive film (VCP) containing 70 mg of N-9 was investigated in a pharmacokinetic study involving 12 US women. At each of 5 test visits, approximately 1 month apart, a single sheet of VCF was inserted at midcycle. Vaginal lavage with normal saline was then performed after 1 of the 5 specified time intervals had elapsed. At 30 minutes, an average of 34.4 mg (49% of the total N-9) could be recovered. After intervals of 1.0, 1.5, and 2.0 hours, 18.5-28.5 mg of N-9 was recovered in lavage fluid. The amount of recovered N-9 dropped significantly to 11.0 mg after 4.0 hours. It is assumed that an N-9 concentration of 0.100 mg/mL is required to immobilize sperm. Thus, the amount of N-9 remaining in the vagina up to 4.0 hours after insertion of VCF is sufficient for contraception. The VCF label states that intercourse may take place 15 minutes after film insertion. Although lavage was not performed at this time point, it can be assumed that at least 49% of the original N-9 would be present. Since this study is limited by the fact that intercourse did not take place, future studies should include postcoital measures of the amount of N-9 persisting at various intervals.