9 Carbamazepine Interactions to Know About

Carbamazepine (Tegretol, Equetro) is an oral medication that can help manage certain kinds of seizure disorders. It can also treat a type of nerve pain called trigeminal neuralgia and help manage symptoms of bipolar disorder. While effective for these conditions, carbamazepine has many interactions.

Carbamazepine interactions happen for several reasons. Many are because of changes to certain liver enzymes (proteins). These enzymes are responsible for breaking down medications in the body, including carbamazepine. This can change its effectiveness and risk of side effects. But carbamazepine is also an enzyme inducer. This means it can change the way other medications are broken down, often making them less effective.

There are many carbamazepine interactions. But which are some of the most important to know about? 

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1. Valproic acid

Valproic acid is a medication used for the prevention of seizures. Valproic acid can lower the level of certain enzymes that break down carbamazepine. This results in higher carbamazepine levels. This can raise your risk of side effects from carbamazepine.

Common side effects may include:

• Dizziness

• Drowsiness

• Balance problems

• Nausea

• Vomiting

The interaction between valproic acid and carbamazepine is two-sided. Carbamazepine can speed up how fast the body breaks down valproic acid. Over time, this combination can lower valproic acid levels and make it less effective.

It’s possible to take both carbamazepine and valproic acid. But you may need dose changes for one or both medications. Your healthcare provider may also check medication levels with blood tests more frequently.

2. Phenytoin

Phenytoin (Dilantin, Phenytek) is a medication used to manage seizures. When taken together with phenytoin, carbamazepine levels are often lower. Less carbamazepine means it may be less effective. At the same time, carbamazepine can also lower phenytoin levels in the body. These changes to both medications can raise your risk of seizures.

Some people do need to take both carbamazepine and phenytoin. You may need a different dose of one or both medications if you’re going to be taking this combination. Your healthcare provider may also check your carbamazepine and phenytoin blood levels more frequently.

3. Certain antidepressants

Taking carbamazepine with certain antidepressants can lead to higher carbamazepine levels. So you may be more likely to experience carbamazepine side effects. Fluoxetine (Prozac) is an antidepressant medication that can have this effect. You may need to take a lower dose of carbamazepine to avoid this interaction with some antidepressants.

Other antidepressant medications — such as bupropion (Wellbutrin XL, Wellbutrin SR), citalopram (Celexa), and tricyclic antidepressants — can also interact with carbamazepine. But in a different way. Carbamazepine can cause levels of these medications to be lower. This could make these antidepressants less effective.

Your healthcare provider may raise your antidepressant dose. They may also prescribe an alternative medication to avoid this interaction.

4. Benzodiazepines

Benzodiazepines, such as alprazolam (Xanax) and clonazepam (Klonopin), are common short-term treatments for anxiety. Carbamazepine can cause these medications to be removed from the body faster. This means benzodiazepines may be less effective.

Your healthcare provider may recommend a benzodiazepine dose change to help manage this carbamazepine interaction. Or they may prescribe an alternative anxiety medication to avoid it altogether.

5. Hormonal birth control

You may be using hormonal birth control to prevent pregnancy or manage other conditions, such as heavy menstrual bleeding. Carbamazepine can make hormonal birth control less effective. This can result in unintended pregnancies and side effects, like breakthrough bleeding.

Not everyone will experience breakthrough bleeding with this carbamazepine interaction. But you should still assume you may not have as much protection from pregnancy. It’s important to use a back-up method of contraception, like condoms, to prevent pregnancy. You can also discuss Paragard (copper intrauterine device) with your healthcare provider. This hormone-free birth control doesn’t interact with carbamazepine.

Using reliable contraception is important while taking carbamazepine. This is because it can cause certain birth defects called neural tube defects if pregnant women are exposed to it. These are birth defects of the brain or spinal cord — like spina bifida. Discuss your birth control options with your healthcare provider.

6. Atypical antipsychotics

Atypical antipsychotics, such as quetiapine (Seroquel) and aripiprazole (Abilify), are prescribed for various mental health conditions. These include schizophrenia, bipolar disorder, and depression. Carbamazepine can lead to lower levels of these medications. This can make them less effective. Some antipsychotics can also raise carbamazepine levels, making side effects more likely.

Many people can still take carbamazepine and antipsychotics. Your healthcare provider may wait to see what happens after you start carbamazepine. They may recommend a higher antipsychotic dose or a lower carbamazepine dose. But if you’re having trouble tolerating the combination, they may recommend an alternative medication.

7. Warfarin

Warfarin (Coumadin, Jantoven) is prescribed to prevent and treat blood clots. It’s notorious for having many interactions. Carbamazepine can lower warfarin levels in the body. This can make warfarin less effective, raising the risk of blood clots.

Warfarin is monitored using a blood test called an international normalized ratio (INR). Your healthcare provider will likely watch your INR level more closely if you take both medications. They may recommend raising your warfarin dose, especially when you first start carbamazepine.

8. Grapefruit juice

Carbamazepine doesn't just interact with medications. It can interact with some dietary items as well. Grapefruit and grapefruit juice block the enzyme that breaks down carbamazepine. This can result in higher carbamazepine levels in your body, and a greater risk for side effects.

There’s no official recommendation on how much grapefruit or grapefruit juice is OK to consume while taking carbamazepine. It’s best to discuss safe amounts with your healthcare provider first. But they may recommend you avoid this citrus fruit.

9. Alcohol

Many medications interact with alcohol. Often, alcohol worsens medication side effects, like sleepiness and dizziness. This is the case if you mix carbamazepine and alcohol. Alcohol can also be a trigger for seizures. Discuss any alcohol use with your healthcare provider.

There’s no hard rule about how much alcohol is OK to drink with carbamazepine. Your healthcare provider will let you know if there’s a safe amount you can drink.

When should I contact my healthcare provider about a carbamazepine interaction?

Carbamazepine interacts with many different medications. So taking as few medications as are needed can lower your risk of carbamazepine interactions. Discuss new medications with your healthcare provider and pharmacist. Together, you can choose medications that are less likely to interact.

Keep an accurate and updated medication list. The medication list should include prescription medications. And it should include over-the-counter medications, vitamins, and supplements. Share this list with your healthcare provider and pharmacist. This way, they can check for potential interactions. They can also make recommendations about how to manage or avoid them.

If you think you’re experiencing a carbamazepine interaction, contact your healthcare provider right away. Interaction symptoms may include new or worse side effects. They can also include a return of symptoms of your health condition.

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Written by:

Nicole E. Cieri-Hutcherson, PharmD, BCPS, NCMP

Nicole E. Cieri-Hutcherson, PharmD, BCPS, NCMP, has over a decade of experience as a pharmacist, professor, and researcher. She was a full-time clinical professor in the pharmacy practice department at D’Youville School of Pharmacy before subsequently joining the faculty of the pharmacy practice department at the University at Buffalo School of Pharmacy and Pharmaceutical Sciences.

Edited by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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