Selected Anticonvulsants; Barbiturates/Contraceptives Interactions

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Serious. These medicines may interact and cause very harmful effects. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

When these two medicines are taken together, your body may process the estrogen in birth control pills more quickly.

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.

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.Emergency contraceptives may be less effective also. You may need a larger dose than normal. Discuss the dose and the need to confirm that you do not become pregnant with a pregnancy test with your healthcare professional.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.

View Reference
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CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.