Anticonvulsants that induce hepatic metabolism increase clearance of oral contraceptive hormones and thereby cause contraceptive failure. Gabapentin is not metabolized in humans and has little liability for causing metabolic-based drug-drug interactions. In healthy women receiving 2.5 mg norethindrone acetate and 50 microg ethinyl estradiol daily for three consecutive menstrual cycles, concurrent gabapentin administration did not alter the steady-state pharmacokinetics of either hormone. Thus, gabapentin is unlikely to cause contraceptive failure.
