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Influence of losigamone on the pharmacokinetics of a combined oral contraceptive in healthy female volunteers.

OBJECTIVES
The influence of the new antiepileptic drug losigamone (CAS 112856-44-7/123783-52-8) on the pharmacokinetics of a combined oral contraceptive containing ethinylestradiol (CAS 57-63-6) and levonorgestrel (CAS 797-63-7) was investigated in 16 healthy women.


METHODS
This phase I study consisted of 3 periods with an uncontrolled first period and a double-blind, placebo-controlled, cross-over design in the second and third period. All subjects received a single dose of 200 mg losigamone (1 tablet) in period 1 (on day 14) as well as multiple doses of losigamone (3 tablets = 600 mg per day) or placebo for 15 days in periods 2 and 3. During all three periods an oral contraceptive containing 30 microg ethinylestradiol and 150 microg levonorgestrel was given. Single-dose pharmacokinetics was investigated on day 14 of period 1. Multiple-dose pharmacokinetic investigations were performed on day 15 of periods 2 and 3. The samples were assayed to derive pharmacokinetic data of ethinylestradiol and levonorgestrel. In addition, the concentrations of losigamone racemate (AO-33) and its enantiomers AO-242 and AO-294 were determined in these samples.


RESULTS
The mean values of the pharmacokinetic parameters AUC and Cmax of ethinylestradiol and levonorgestrel after multiple-dose treatment with losigamone or placebo were quite similar and met the criteria for bioequivalence. The 90% confidence intervals of the log-transformed ratios of the geometric means of the primary pharmacokinetic variables were included in the respective acceptance ranges of 80% to 125% (AUC) and 70% to 143% (Cmax).


CONCLUSIONS
The study demonstrated that multiple doses of losigamone did not influence the multiple dose kinetics of ethinylestradiol and levonorgestrel. The single- and multiple-dose kinetics of 200 mg losigamone and its enantiomeres did not differ from each other in a significant way. The combination of losigamone and the combined oral contraceptive was well tolerated and no serious adverse events occurred. It can be stated that the antiepileptic drug losigamone and the combined contraceptive do not interact each others metabolism.