Everywhere keeps saying that Topamax "might" make the contraceptives less effective but no one lists how "likely" this is to occur. My GF is taking about 125 mgs a day. She’s been taking both pills for about 3 years and we haven’t had any problems. Neither her doctor nor neurologist said anything about it to her.
{ 2 comments… read them below or add one }
at doses of 200mg per day or less, topamax has no effect on oral contraceptives. see study
results:
At dosages of 200 mg or less, topiramate as daily monotherapy in healthy volunteers does not have a significant interaction with oral contraceptives, researchers reported here on April 1st at the 55th Annual Meeting of the American Academy of Neurology.
results of a 2004 study:
Unlike old AEDs such as phenytoin and carbamazepine, topiramate is a mild inducer and, currently, the only interaction observed as a result of induction by topiramate is that with ethinylestradiol. Topiramate only increases the oral clearance of ethinylestradiol in an oral contraceptive at high dosages (>200 mg/day)
I have read that Topamax affects birth control at does of 400 mg or more daily. I have also read that it MAY reduce the effectiveness of birth control at does of 150mg or more, but no definitive conclusions could be made. I use to take both Topamax (100mg) and Yasmin and had no problems, but that was just me.