Vigabatrin appears not to alter pharmacokinetics of ethinyloestradiol or levonorgestrel given as a combined oral contraceptive
Clinical evidence,mechanism, importance and management
Vigabatrin 3 g daily had no statistically significant effect on pharmacokinetics of ethinylestradiol and levonorgestrel in 13 healthy women given a single dose of a combined oral contraceptive (ethinylestradiol/levonorgestrel 30/150 micrograms); although 2 of women had a 39 % and a 50 % fall in AUC of ethinylestradiol
This study would seem to confirm lack of reports of an interaction between oral contraceptives and vigabatrin, but authors of report introduce a small note of caution because it is not clear whether reduced ethinylestradiol AUCs seen in two of women resulted from an interaction or were simply normal individual variations (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 vigabatrin does not induce liver enzymes and causes no reduction in ethinylestradiol or progestogens (See reference number 2). No special precautions are recommended.
Bartoli A,Gatti G, Cipolla G, Barzaghi N, Veliz G, Fattore C, Mumford J, Perucca E. A double-blind, placebo-controlled study on the effect of vigabatrin on in vivo parameters of hepaticmicrosomal enzyme induction and on the kinetics of steroid oral contraceptives in healthy female volunteers. Epilepsia (1997) 38, 702–7.
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).