Sometimes one kind of medicine changes the way another kind of medicine works in the body. If two kinds of medicine affect each other, the doctor may prescribe something else or change the amount to be taken.

Topamax makes birth control pills less effective, so the chances of becoming pregnant are greater. Women who use pills for birth control should talk to the doctor who prescribed them right away if they start taking Topamax. The same is true for some other forms of birth control such as Depo-Provera or implants. Topamax does not affect barrier types of birth control, like condoms, IUDs, and diaphragms.

Topamax also affects the way the body handles phenytoin (Dilantin, Phenytek), so if you take phenytoin, ask your doctor whether you should change your dose of phenytoin.

How do other medicines affect Topamax?
Your body gets rid of Topamax quicker if you are also taking certain seizure medicines, such as:

• carbamazepine (Tegretol, Tegretol XR, Carbatrol)
• phenytoin (Dilantin, Phenytek)
• phenobarbital
• primidone (Mysoline)

If this applies to you, your doctor may plan to give you more Topamax than you would otherwise take.

Any time one of your doctors suggests starting or stopping a prescription, be sure to ask what effect it might have on the Topamax, and whether the dosage should be increased or decreased.

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