.I've heard that Topamax does interfer with B/C but then I read a study... that said under 150mg it does not effect BC. My neurologist says low doses (under 150mg) will NOT effect Yaz but my OBGYN was wishy washy on whether or not it would. Any help? I am on 50 mg (25mg AM / 25mg pm)
Yes, it may be decreased.
READ THE FOLLOWING IMPORTANT INFORMATION.
Interactions between your selected drugs
ethinyl estradiol ↔ topiramate
Applies to: Yasmin (drospirenone/ethinyl estradiol), Topamax (topiramate)
ADDITIONAL CONTRACEPTION RECOMMENDED: Efficacy of oral contraception may be decreased by concomitant use with topiramate. The mechanism of action appears to be increased metabolism of the estrogenic component of the oral contraceptive. In a pharmacokinetic study with topiramate 800 mg/day, ethinyl estradiol clearance increased by 47% (range 13% to 107%), while norethindrone was unaffected. Although this has not been reported with mestranol, the likelihood of an interaction should be considered.
MANAGEMENT: Patients taking oral contraceptives and topiramate should be warned of the potential for decreased efficacy of the oral birth control, counseled about the use of additional pregnancy prevention methods, and advised to report any changes in bleeding patterns to their clinician. Some experts have recommended a higher dose contraceptive; however, no specific recommendations are available. Intrauterine systems are unlikely to be significantly affected because of their local action.
Other drugs that your selected drugs interact with
* Topamax (topiramate) interacts with more than 200 other drugs.
* Yasmin (drospirenone/ethinyl estradiol) interacts with more than 400 other drugs.
I HOPE THIS HELPS YOU.
Topamax is an "enzyme inducer" which means that it speeds up the metabolism of estrogens. This can reduce the contraceptive effect of estrogen containing birth control pills such as Yasmin.
You would be wise to consider another method of contraception.
There is unfortunately no black and white answer to this questions because people metabolize drugs differently based on their physiology. The paper makes reference to a dosage of ethinyl estradiol: "Start with an OC pill with estrogen 50 μg at least and, if breakthrough bleeding occurs, an even higher estrogen dose may be needed." I'd send this paper to your OB/GYN and have him/her review it and then make an appointment to discuss options. The issue is having a high enough dose of hormone in your circulation. If you are more concerned about becoming pregnant, use a backup method until you come up with a better dosing regimen.
To my knowledge, topiramate does not decrease efficacy of Plan B because of the high dose of hormones in the pill.
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