The objectives of this study were to determine the amount of nonoxynol-9 (N-9) remaining in the vagina 30 min and 1, 1.5, 2, and 4 h after vaginal insertion of a single sheet of VCF containing 70 mg N-9 and to compare these results to the manufacturer's instructions for use of this product. A new method of vaginal lavage was used to obtain samples for N-9 determination. This was an open-label, noncomparative, pharmacokinetic study in 12 healthy women volunteers not at risk for pregnancy. The study consisted of a screening visit followed by five test visits approximately 1 month apart and a final visit 1 week after all test visits were completed. At each test visit, the investigator inserted a single sheet of VCF in the vagina of the volunteer at midcycle. The volunteer remained in the clinic and underwent vaginal lavage with normal saline after one of five specified time intervals had elapsed. The sequence of the intervals completed by each volunteer was determined by randomization. When undissolved film was found in the vagina, it was removed prior to lavage and assayed for N-9 content separately from that recovered in lavage fluid. It was assumed that the N-9 in undissolved film would not contribute significantly to sperm immobilization. Between 18.5 and 28.5 mg of N-9 were recovered in lavage fluid after intervals of 0.5, 1, 1.5, and 2 h. These levels did not differ statistically (p > 0.05). The amount of N-9 recovered dropped significantly at 4 h to 11.0 mg. If it is assumed that an N-9 concentration of 0.100 mg/mL is required to immobilize sperm in vitro, this study suggests that the amount of N-9 remaining in the vagina in the form of dissolved film up to 4 h after insertion of VCF is sufficient to immobilize sperm. The lavage procedure may not have recovered all N-9 remaining in the vagina. However, intercourse did not take place between insertion and lavage; if it had, the proportion of the film remaining undissolved and the total amount N-9 remaining in the vagina at the time of examination might have been affected.
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.