Carbamazepine with Efavirenz Interaction Details
Brand Names Associated with Carbamazepine
- Carbamazepine
- Carbatrol®
- Epitol®
- Equetro®
- Tegretol®
- Tegretol®-XR
- Teril®
Brand Names Associated with Efavirenz
- Atripla® (as a combination product containing Efavirenz, Emtricitabine, Tenofovir)
- Efavirenz
- Sustiva®
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 25, 2023
Interaction Effect
Reduced efavirenz plasma concentrations and risk of diminished therapeutic effect of efavirenz, including loss of virologic response and possible resistance
Interaction Summary
Efavirenz is primarily metabolized by CYP3A4 isozymes, and concomitant use with drugs that induce CYP3A4, such as carbamazepine, may lead to decreased efavirenz plasma concentrations and possible loss of virologic response or drug resistance development. Therefore, concomitant use of carbamazepine and efavirenz is contraindicated. Coadministration of carbamazepine and efavirenz resulted in lowered exposures and plasma concentrations of both carbamazepine and efavirenz .
Severity
Contraindicated
Onset
Unspecified
Evidence
Established
How To Manage Interaction
Coadministration of carbamazepine and efavirenz is contraindicated as it may lead to decreased efavirenz plasma concentrations, loss of virologic response, and possible resistance development.
Mechanism Of Interaction
Induction of CYP3A4-mediated efavirenz metabolism by carbamazepine
Literature Reports
A) Coadministration of carbamazepine and efavirenz resulted in decreased exposure and plasma concentrations of both carbamazepine and efavirenz in pharmacokinetic studies. In 12 subjects, efavirenz (600 mg orally daily for 14 days) decreased the plasma Cmax, AUC, and Cmin of carbamazepine (200 mg/day for 3 days, 200 mg twice daily for 3 days, then 400 mg/day for 29 days) by an average of 20% (90% CI, 15% to 24%), 27% (90% CI, 20% to 33%), and 35% (90% CI, 24% to 44%), respectively. In 14 subjects, carbamazepine (200 mg/day for 3 days, 200 mg twice daily for 3 days, then 400 mg/day for 15 days) decreased the plasma Cmax, AUC, and Cmin of efavirenz (600 mg orally daily for 35 days) by an average of 21% (90% CI, 15% to 26%), 36% (90% CI, 32% to 40%), and 47% (90% CI, 41% to 53%), respectively .
Carbamazepine Overview
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Carbamazepine is used alone or in combination with other medications to control certain types of seizures in people with epilepsy. It is also used to treat trigeminal neuralgia (a condition that causes facial nerve pain). Carbamazepine extended-release capsules (Equetro brand only) are also used to treat episodes of mania (frenzied, abnormally excited or irritated mood) or mixed episodes (symptoms of mania and depression that happen at the same time) in patients with bipolar I disorder (manic-depressive disorder; a disease that causes episodes of depression, episodes of mania, and other abnormal moods). Carbamazepine is in a class of medications called anticonvulsants. It works by reducing abnormal electrical activity in the brain.
Efavirenz Overview
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Efavirenz is used along with other medications to treat human immunodeficiency virus (HIV) infection. Efavirenz is in a class of medications called non-nucleoside reverse transcriptase inhibitors (NNRTIs). It works by decreasing the amount of HIV in the blood. Although efavirenz does not cure HIV, it may decrease your chance of developing acquired immunodeficiency syndrome (AIDS) and HIV-related illnesses such as serious infections or cancer. Taking these medications along with practicing safer sex and making other life-style changes may decrease the risk of transmitting (spreading) the HIV virus to other people.
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Definitions
Severity Categories
Contraindicated
These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.
Major
This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.
Moderate
This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.
Minor
While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.
Onset
Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.
Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.
Evidence
Level of documentation of the interaction.
Established: The interaction is documented and substantiated in peer-reviewed medical literature.
Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.
How To Manage The Interaction
Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.
It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.
Mechanism Of Interaction
The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.
Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.
Where Does Our Information Come From?
Information for our drug interactions is compiled from several drug compendia, including:
The prescribing information for each drug, as published on DailyMED, is also used.
Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.
The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.