Drug interactions
Carbamazepine + Phenobarbital
Severity: Moderate
Carbamazepine and Phenobarbital: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Phenobarbital commonly lowers carbamazepine concentrations, which may lead to breakthrough seizures. Additive sedation is also possible.
What this interaction means in plain words
Carbamazepine and Phenobarbital can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Phenobarbital induces CYP3A4, increasing carbamazepine clearance.
What to do
Monitor carbamazepine concentrations and seizure control and increase the dose if needed. Reassess when phenobarbital is started or stopped.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Carbamazepine
- Artemether / lumefantrine + Carbamazepine Contraindicated
- Cabotegravir + Carbamazepine Contraindicated
- Carbamazepine + Delamanid Contraindicated
- Carbamazepine + Dienogest / estradiol valerate Contraindicated
- Carbamazepine + Doravirine Contraindicated
- Carbamazepine + Elbasvir / grazoprevir Contraindicated
Frequently asked questions
Can I take Carbamazepine with Phenobarbital?
MediHelp rates the interaction as moderate. Carbamazepine and Phenobarbital can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Phenobarbital commonly lowers carbamazepine concentrations, which may lead to breakthrough seizures. Additive sedation is also possible.
How serious is the interaction between Carbamazepine and Phenobarbital?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor carbamazepine concentrations and seizure control and increase the dose if needed. Reassess when phenobarbital is started or stopped.
What other medicines interact with Carbamazepine?
MediHelp also lists interactions of Carbamazepine with, for example, Artemether / lumefantrine, Cabotegravir, Delamanid. The full list is on the Carbamazepine page.
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