Pharmacodynamic and pharmacokinetic evaluation of coadministration of lacosamide and an oral contraceptive (levonorgestrel plus ethinylestradiol) in healthy female volunteers

Abstract

To determine whether the antiepileptic drug lacosamide affects the pharmacokinetics or pharmacodynamics of a combined oral contraceptive (OC; ethinylestradiol 0.03mg plus levonorgestrel 0.15mg). This was an open-label trial in healthy female volunteers. Eligible women entered cycle 1 of the trial on the first day of menstruation. Cycle 1 was a medication-free, run-in phase of approximately 28days to confirm that normal ovulation occurred. Volunteers with confirmed ovulation entered the subsequent cycle and started taking OCs. After establishing ovulation suppression (defined as progesterone serum concentration <5.1nm on day 21 of the menstrual cycle) in volunteers taking the OCs in cycle 2, lacosamide 400mg/day was administered concomitantly in the subsequent cycle (cycle 3). The pharmacokinetic parameters of area under the concentration-time curve (AUC), maximum steady-state plasma drug concentration (Cmax ), and time to maximum concentration (tmax ) were measured for the OC components and lacosamide. A total of 37 volunteers completed cycle 1, and 32 completed cycle 2. In each of the 31 volunteers who completed the trial (through cycle 3), pharmacodynamic assessment showed progesterone serum concentration was <5.1nm on day 21 of cycle 2, when the OC was administered alone, and on day 21 of cycle 3, when lacosamide was administered concomitantly. The AUC of ethinylestradiol alone versus together with lacosamide was 1,067±404 versus 1,173±330pgh/ml. Corresponding values of Cmax were 116.9±48.8 versus 135.7±28.6pg/ml. For levonorgestrel, the AUC alone was 74.2±21.4 versus 80.9±18.5ngh/ml with lacosamide. Corresponding values of Cmax were 6.7±1.9 versus 7.4±1.5ng/ml. The AUC and Cmax point estimates and almost all 90% confidence intervals (except for Cmax of ethinylestradiol) for ethinylestradiol and levonorgestrel (with and without lacosamide) were within the conventional bioequivalence range, and no relevant changes in tmax were observed for ethinylestradiol (1.5±0.6h alone vs. 1.4±0.7h with lacosamide) or for levonorgestrel (1.5±1.0h alone vs. 1.1±0.6h with lacosamide). Lacosamide pharmacokinetics were consistent with those observed in previous studies of lacosamide alone, with values for AUC of 113.5±20.7μgh/ml, Cmax of 13.8±2.2μg/ml, and tmax of 1.1±0.4h. Lacosamide and an OC containing ethinylestradiol and levonorgestrel have low potential for drug-drug interaction; therefore, coadministration of the two drugs is unlikely to result in contraceptive failure or loss of seizure control.