ICWCNS, Basel, and if1.P.A.S. SA, Stubio, Switzerland Summary: Purpose: To evaluate the effect of oxcarbazepine (OCBZ) on the pharmacokinetic profile of steroid oral contraceptives.Methods: Twenty-two healthy women aged 18-44 years were recruited, and 16 of them completed the study. By using a randomized double-blind crossover design, each woman was studied in two different menstrual cycles, during which placebo or OCBZ (maintenance dosage, 1,200 mglday) was given in randomized sequence for 26 consecutive days with a washout of at least one cycle in between. A steroid oral contraceptive containing 50 p,g ethinylestradiol (EE) and 250 tJ-g levonorgestrel (LN) was taken for the first 21 days of each cycle. Plasma concentrations of EE and LN were measured by gas chromatography-mass spectrometry in samples collected at regular intervals on days 21-23 of each cycle.Results: Compared with placebo, areas under the plasma concentration curves (AUC,,,,, geometric means) decreased by 47% for both EE (from 1,677 to 886 pgWml; p < 0.01) and LN(from 137 to 73 ngWml; p < 0.01), during OCBZ treatment. Peak plasma EE concentrations decreased from 180 pg/ml during the placebo cycle to 117 pg/ml during the OCBZ cycle (p < O.Ol), whereas peak plasma LN concentrations decreased from 10.2 to 7.7 ng/ml (p < 0.01). The half-lives of EE and LN also decreased from 13.6 to 7.9 h (p < 0.01) and from 28.8 to 15.8 h, respectively (p i 0.01).Conclusions: OCBZ reduces plasma concentrations of the estrogen and progestagen components of steroid oral contraceptives, presumably by stimulating their CYP3A-mediated metabolism in the liver or gastrointestinal tract or both. Because this may lead to a decreased efficacy of the contraceptive pill, women treated with OCBZ should receive preferentially a high-dosage contraceptive and should be monitored for signs of reduced hormonal cover.

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Oxcarbazepine treatment over 6 months does not display any differential effects on cognitive function and intelligence in children and adolescents with newly diagnosed partial seizures relative to standard antiepileptic drug therapy. No impairment in cognitive function was observed in any treatment group over a 6-month period.

In this study, high-dose oxcarbazepine was significantly more effective than low-dose oxcarbazepine in controlling partial seizures in infants and very young children.