The effect of ezogabine on the pharmacokinetics of an oral contraceptive agent.

OBJECTIVES

Ezogabine (EZG) is a potassium-channel opener that has been approved as adjunctive treatment for partial-onset seizures in adults with epilepsy. This Phase I clinical study evaluated the pharmacokinetics (PK), safety, and tolerability of coadministration of EZG and a combined oral contraceptive (OC).

METHODS

An open-label drug-interaction study was conducted in healthy, female volunteers aged 18 - 55 years with regular menstrual cycles. The effects of steady-state 750 mg EZG on the PK of a combined OC agent containing 1 mg norethindrone and 0.035 mg ethinyl estradiol were evaluated, along with the effect of the contraceptive hormones on EZG PK. Safety was evaluated by clinical laboratory, vital sign, electrocardiogram, physical examination, and adverse event (AE) assessments.

RESULTS

Of 30 enrolled volunteers, 25 completed all treatments. OC did not affect the PK of EZG. EZG increased norethindrone area under the concentration-time curve (AUC) by 28%, with no change in the maximum plasma concentration (Cmax). Ethinyl estradiol Cmax was 21% lower with no change in AUC. The majority of AEs were mild in severity, with the most commonly reported being gastrointestinal disorders and nervous system disorders. No deaths or serious AEs were reported in this study. Five volunteers discontinued treatment due to AEs.

CONCLUSIONS

EZG did not have any clinically relevant impact on exposure of OC hormones in this study, and the OC hormones did not alter EZG PK parameters. This study provides PK evidence that doses of EZG and OCs do not need to be altered when co-administered.