Sometimes one kind of medicine changes the way another kind of medicine works in the body. This is true not only for prescription medicines, but also for medicines you just pick up off the shelf at the store. It’s also true for herbal products, vitamins, a few kinds of food, and even cigarettes!

Any time a doctor suggests a new prescription, be sure to talk about what other medicines you are already using. If two kinds of medicine affect each other, the doctor may want to prescribe something else or change the amount to be taken.

Does carbamazepine affect other medicines?
Carbamazepine 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 carbamazepine. The same is true for some other forms of birth control such as Depo-Provera and implants. Carbamazepine does not affect barrier types of birth control, like condoms, IUDs, and diaphragms.

Carbamazepine also affects the way the body handles many other seizure medicines. Some of these are:

• Depakote (valproic acid)
• Dilantin or Phenytek (phenytoin)
• Klonopin (clonazepam)
• Topamax (topiramate)

Do other medicines affect carbamazepine?
Yes, some medicines can cause carbamazepine to build up in the blood. Having too much carbamazepine in the blood makes people feel dizzy, unsteady, or sleepy. Some of the medicines and other things that may have this effect include:

• Depakote and other valproate seizure medicines
• some medicines for high blood pressure, including Cardizem (diltiazem) and verapamil
• Prozac (fluoxetine)
• certain antibiotics, including erythromycin
• cimetidine (Tagamet, also available without a prescription)
• several types of anti-fungus medications
• painkillers Darvon and Darvocet
• grapefruit juice

On the other hand, some medicines reduce the amount of carbamazepine in the blood. More seizures may occur unless a higher dosage of carbamazepine is taken. Medicines that may have this effect include:

• Dilantin or Phenytek (phenytoin)
• Trileptal (oxcarbazepine)
• Felbatol (felbamate)
• phenobarbital
• Mysoline (primidone)