Drug interactions
Phenobarbital + Verapamil
Severity: Moderate
Phenobarbital and Verapamil: 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 can lower verapamil concentrations, causing reduced antihypertensive or antiarrhythmic effect. The effect builds over days to weeks and fades after phenobarbital withdrawal.
What this interaction means in plain words
Phenobarbital and Verapamil 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 the metabolism of verapamil.
What to do
Monitor heart rate and blood pressure and increase verapamil as needed. Reduce the dose again if phenobarbital is discontinued.
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 Verapamil
- Dofetilide + Verapamil Contraindicated
- Flibanserin + Verapamil Contraindicated
- Lomitapide + Verapamil Contraindicated
- Lonafarnib + Verapamil Contraindicated
- Pimozide + Verapamil Contraindicated
- Acebutolol + Verapamil Major
Frequently asked questions
Can I take Phenobarbital with Verapamil?
MediHelp rates the interaction as moderate. Phenobarbital and Verapamil 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 can lower verapamil concentrations, causing reduced antihypertensive or antiarrhythmic effect. The effect builds over days to weeks and fades after phenobarbital withdrawal.
How serious is the interaction between Phenobarbital and Verapamil?
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 heart rate and blood pressure and increase verapamil as needed. Reduce the dose again if phenobarbital is discontinued.
What other medicines interact with Verapamil?
MediHelp also lists interactions of Verapamil with, for example, Dofetilide, Flibanserin, Lomitapide. The full list is on the Verapamil page.
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