Effect of sexual intercourse on the absorption of levonorgestrel after vaginal administration of 0.75 mg in Carraguard gel: a randomized, cross-over, pharmacokinetic study.

ABSTRACT

BACKGROUND: The Population Council studied a pre-coital contraceptive microbicide vaginal product containing levonorgestrel (LNG) as active component and Carraguard gel as a vehicle (Carra/LNG gel) for couples who engage in occasional unplanned intercourse. The objective of this study was to evaluate the effect of sexual intercourse after vaginal application of Carra/LNG gel on serum levels of LNG in women and to assess LNG absorption by the male partner. STUDY DESIGN: This was a randomized, cross-over, pharmacokinetic study including an abstinence arm and an arm in which couples engaged in sexual intercourse between 2 and 4 h after gel application. In each study arm, each woman received a single application of Carra/LNG gel (0.75 mg in 4 mL gel) followed by serial blood samples taken at 0, 1, 2, 4, 8, 24 and 48 h after gel application for LNG measurements. In the intercourse arm, LNG was measured in blood samples taken from the male partner before intercourse and at 4, 8 and 24 h after gel application in the female partner. RESULTS: Time concentration curves for serum LNG levels showed a mean C(max) of 7.8+/-5.5 and 8.3+/-5.7 nmol/L, a mean T(max) of 6.2+/-5.9 and 7.5+/-5.7, and comparable area under the curve for the intercourse and abstinence arm, respectively. Pharmacokinetic parameters presented large variability between subjects, but excellent reproducibility within each subject. LNG was undetectable in 10 out of 12 male partners. CONCLUSION: Sexual intercourse does not appear to interfere with vaginal absorption of LNG after application of a Carra/LNG gel. A vaginal pre-coital contraceptive gel is feasible.