AN INVESTIGATION INTO THE EFFECT OF TENIDAP SODIUM ON THE PHARMACOKINETICS OF A COMBINED ORAL-CONTRACEPTIVE

1 The effects of tenidap sodium and placebo on the pharmacokinetics of a combined oral contraceptive (Microgynon 30(R)) were evaluated in 18 healthy premenopausal women in a double-blind, cross-over study lasti ng two menstrual cycles.2 Tenidap (120 mg day(-1)) or placebo was give n for 11 days, starting within 4 days of menstruation and Microgynon 3 0(R), containing levonorgestrel (150 mu g) and ethinyloestradiol (30 m u g), was administered on day 10 of tenidap therapy. 3 The mean maximu m plasma levonorgestrel concentrations (C-max), time to C-max (t(max)) and area under the plasma time-concentration curves (AUC(O,t)) did no t differ between subjects given tenidap or placebo, The C-max, t(max) and AUC(O,t) values for ethinyloestradiol did not differ between tenid ap and placebo recipients. Only the ethinyloestradiol C showed a signi ficant difference (P = 0.02) max between menstrual cycles 1 and 2 (252 .9 pg ml(-1) and 271.3 pg ml(-1), respectively). 4 Co-administration o f tenidap and Microgynon 30(R) was well tolerated and no subject withd rew from the study because of side-effects. There were no side-effects considered to be related to tenidap and no clinically significant lab oratory abnormalities were considered to be related to treatment. 5 Th e results of the study suggest that the pharmacokinetics of the oestro gen and progestin components of the oral contraceptive Microgynon 30(R ) are unlikely to be affected by concomitant administration of tenidap .