Drug interactions
Mefloquine + Phenobarbital
Severity: Major
Mefloquine and Phenobarbital: major 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 induces hepatic enzymes and may lower mefloquine concentrations, reducing prophylactic or treatment efficacy. Mefloquine may also lower the seizure threshold and thus antagonize the anticonvulsant effect of phenobarbital.
What this interaction means in plain words
Mefloquine and Phenobarbital can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Induction of CYP3A4 by phenobarbital increases mefloquine clearance, and mefloquine has pharmacodynamic neuropsychiatric and proconvulsant effects.
What to do
Prefer an alternative antimalarial in patients on phenobarbital. If used, monitor for malaria breakthrough and seizure control.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Mefloquine
- Arsenic trioxide + Mefloquine Contraindicated
- Dronedarone + Mefloquine Contraindicated
- Ibutilide + Mefloquine Contraindicated
- Levoketoconazole + Mefloquine Contraindicated
- Mefloquine + Nilotinib Contraindicated
- Mefloquine + Pimozide Contraindicated
Frequently asked questions
Can I take Mefloquine with Phenobarbital?
MediHelp rates the interaction as major. Mefloquine and Phenobarbital can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Phenobarbital induces hepatic enzymes and may lower mefloquine concentrations, reducing prophylactic or treatment efficacy. Mefloquine may also lower the seizure threshold and thus antagonize the anticonvulsant effect of phenobarbital.
How serious is the interaction between Mefloquine and Phenobarbital?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Prefer an alternative antimalarial in patients on phenobarbital. If used, monitor for malaria breakthrough and seizure control.
What other medicines interact with Mefloquine?
MediHelp also lists interactions of Mefloquine with, for example, Arsenic trioxide, Dronedarone, Ibutilide. The full list is on the Mefloquine page.
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