LACK OF INTERACTION BETWEEN ORLISTAT AND ORAL-CONTRACEPTIVES

Objectives: Orlistat, a potent and selective inhibitor of gastrointest inal lipases, is designed for the treatment of obesity. A double-blind , randomised, placebo-controlled, 2-way crossover study investigated t he possible influence of orlistat on the ovulation-suppressing action of combination oral contraceptives (OC). Methods: After an 8-day run-i n prior to the first of two consecutive menstrual cycles (Day 1 was th e first day of menstruation), two groups of 10 healthy women, 20-27 ye ars of age and on a stable regimen with OCs, received either 120 mg or listat t.i.d. or placebo t.i.d. on Days 1-23 of the first cycle, and, separated by a placebo washout period on Days 24-28, the alternative t reatment on Days 1-23 of the second cycle. In both cycles, serum lutei nizing hormone (LH) was measured on Days 12-16 and progesterone on Day s 12, 16, 19-23. Results: The geometric means of time-averaged concent rations (Days 12-16 for LH and Days 19-23 for progesterone) in the cyc les with orlistat and placebo, respectively, and the one-sided 95% con fidence region for the mean in the cycle with orlistat were 1.92, 2.03 and < 2.23 IU l(-1) for LH and 0.147, 0.145 and < 0.176 mu g l(-1) fo r progesterone. The one-sided 95% confidence region for the ratio (orl istat/placebo) of geometric means was < 1.06 for LH and < 1.11 for pro gesterone. Conclusion: During normal ovulation the peak serum concentr ation of LH is above 30 IU l(-1) around Day 14 of the cycle, and that of progesterone exceeds 3 mu g l(-1) around day 21. The 95% confidence regions for the means, as well as all individual concentrations, were below these limits. It was concluded that orlistat did not influence the ovulation suppressing action of oral contraceptives.