Carbamazepine with Vigabatrin Interaction Details

Brand Names Associated with Carbamazepine

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated Nov 25, 2023

Interaction Effect

Carbamazepine toxicity (ataxia, nystagmus, diplopia, headache, vomiting, apnea, seizures, coma)

Interaction Summary

In a study of sixty-six patients with epilepsy, when vigabatrin was added to carbamazepine therapy the average carbamazepine serum concentrations increased 24.2%. A strong negative correlation between the value of the increase and the initial level of carbamazepine concentration after vigabatrin addition also was revealed in this study.

Severity

Major

Onset

Delayed

Evidence

Probable

How To Manage Interaction

When vigabatrin is added to carbamazepine therapy, concentration of carbamazepine should be monitored and the dose of carbamazepine should be adjusted accordingly.

Mechanism Of Interaction

Decreased carbamazepine metabolism

Literature Reports

A) Sixty-six patients with epilepsy were evaluated for the changes in carbamazepine concentration following vigabatrin addition. All patients had simple or complex partial seizures, and all were drug-resistant. Vigabatrin was added as a second drug after long-term (at least 3 months) carbamazepine monotherapy and was administered in increasing doses. Carbamazepine concentrations prior to vigabatrin addition was 9.41 mcg/ml (range 4.33 to 13.05 mcg/ml). After addition of vigabatrin the mean carbamazepine concentration increased to 11.31 mcg/ml (range 6.88 to 18.57 mcg/ml). The average increase in carbamazepine concentration was 24.2%. An increase in carbamazepine concentration by at least 10% occurred in 46 out of 66 patients, i.e. 69.7%, after vigabatrin therapy. Twenty-four patients (36.4%) responded with a carbamazepine level of at least 12 mcg/ml. Carbamazepine concentration in this group ranged from 11.99 to 18.57 mcg/ml whereas the carbamazepine concentration before vigabatrin therapy was 10.57 mcg/ml (range 6.59 to 13.05 mcg/ml). No significant relationship was found between vigabatrin dosage and the percentile change in carbamazepine concentration after the addition of vigabatrin. There was a strong negative correlation between the percentile increase in carbamazepine concentration and initial carbamazepine concentration .

B) Vigabatrin produces a statistically significant increase in the plasma clearance of carbamazepine (CBZ) when the two drugs are given simultaneously. Fifteen patients with refractory partial epilepsy and receiving vigabatrin as add-on therapy were studied. Treatment 1 consisted of an initial period with CBZ monotherapy. Treatment 2 consisted of CBZ in combination with vigabatrin. CBZ monotherapy was given for 3-12 months with monitoring of CBZ plasma concentrations. After an initial period, patients received open add-on treatment with vigabatrin 1500 mg/day in two divided doses. The initial 1500 mg daily dose of vigabatrin was increased up to a maximum of 4000 mg. The final daily dose of vigabatrin was 2150+/-900 mg, with a range of 1500-4000 mg. The steady-state trough plasma concentration of CBZ was decreased in the presence of vigabatrin, with a mean value of 7.9+/-1.4 vs 6.5+/-2.0 mcg/mL (p less than 0.03), respectively. The L/D ratio of CBZ was significantly decreased from 0.59 +/- 0.20 in monotherapy to 0.45+/-0.15 in combination with vigabatrin (p less than 0.05). CBZ plasma clearances in monotherapy ranged from 40 to 128 mL/h/kg, with a mean value of 78.5+/-25.8 mL/h/kg. When CBZ was combined with vigabatrin there was a marked increase in the plasma clearance of CBZ (56-177 mL/h/kg) with a mean value of 105.8 +/- 38.9 mL/h/kg (P less than 0.01). The plasma clearance of CBZ is increased by 35% in the presence of vigabatrin. Dosing of CBZ and vigabatrin in combination is best adjusted by individual therapeutic drug monitoring .

Carbamazepine Overview

• 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.

Return To Our Drug Interaction Homepage

Feedback, Question Or Comment About This Information?

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:

• Gold Standard Drug Database
• Micromedex
• Lexicomp
• DrugBank

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.