How the interaction occurs:
When these two medicines are taken together, your body may process the estrogen in birth control pills more quickly. Your ability to process some seizure medicines called hydantoins may decrease.
What might happen:
The effects of your birth control pills may decrease and cause breakthrough bleeding, spotting, or pregnancy. If you are taking a product containing phentermine and topiramate for weight loss, you may experience breakthrough bleeding, but it is not expected to decrease the effectiveness of your birth control.If your seizure medicine is a hydantoin, it may be less effective.
What you should do about this interaction:
If you are taking medicine for seizures, talk to your healthcare professional (e.g. doctor or pharmacist) as soon as possible about using a different form of birth control. Contact your doctor if you experience breakthrough bleeding, spotting, or pregnancy, or if you have any seizures.If you are taking a product containing phentermine and topiramate for weight loss, let your doctor know if your bleeding patterns change. It is important to keep taking your birth control AND use a barrier method of contraception while using your phentermine and topiramate.Your healthcare professionals may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.
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