In a controlled study, gabapentin did not alter levels of ethinylestradiol or norethisterone.
Clinical evidence,mechanism, importance and management
Gabapentin 400mg every 8 hrs for 7 days had no effect on AUC of ethinylestradiol or norethisterone in 13 healthy women taking a combined oral contraceptive (ethinylestradiol/norethisterone 50 micrograms/2.5 mg). Ovulation suppression was not assessed (See reference number 1). The Faculty of Family Planning and Reproductive Health Care (FFPRHC) Clinical Effectiveness Unit guidelines on management of hormonal contraceptives and drug interactions state that gabapentin does not induce liver enzymes responsible for metabolism of contraceptive steroids and causes no reduction in ethinylestradiol or progestogens (See reference number 2). Thus,no special contraceptive precautions appear to be required during concurrent use.
Eldon MA,Underwood BA, Randinitis EJ, Sedman AJ. Gabapentin does not interact with acontraceptive regimen of norethindrone acetate and ethinyl estradiol. Neurology (1998) 50, 1146–8.
Faculty of Family Planning and Reproductive Health Care Clinical Effectiveness Unit.FFPRHC Guidance: Drug interactions with hormonal contraception. April 2005. Available at:http://www.ffprhc.org.uk/admin/uploads/DrugInteractionsFinal.pdf (accessed 23/08/07).