Drug interactions
Clarithromycin + Phenobarbital
Severity: Moderate
Clarithromycin 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 induces hepatic and intestinal CYP3A4, which can lower clarithromycin exposure and may reduce antibacterial efficacy. Induction develops over days to weeks and persists after phenobarbital is stopped.
What this interaction means in plain words
Clarithromycin 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 and increases clarithromycin metabolism, lowering its plasma concentrations.
What to do
Monitor clinical response to clarithromycin and consider an alternative antibiotic not dependent on CYP3A4 if treating a serious infection. Note that the 14-hydroxy metabolite proportion may rise.
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 Clarithromycin
- Astemizole + Clarithromycin Contraindicated
- Avanafil + Clarithromycin Contraindicated
- Cisapride + Clarithromycin Contraindicated
- Clarithromycin + Colchicine Contraindicated
- Clarithromycin + Conivaptan Contraindicated
- Clarithromycin + Dihydroergotamine Contraindicated
Frequently asked questions
Can I take Clarithromycin with Phenobarbital?
MediHelp rates the interaction as moderate. Clarithromycin 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 induces hepatic and intestinal CYP3A4, which can lower clarithromycin exposure and may reduce antibacterial efficacy. Induction develops over days to weeks and persists after phenobarbital is stopped.
How serious is the interaction between Clarithromycin 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 clinical response to clarithromycin and consider an alternative antibiotic not dependent on CYP3A4 if treating a serious infection. Note that the 14-hydroxy metabolite proportion may rise.
What other medicines interact with Clarithromycin?
MediHelp also lists interactions of Clarithromycin with, for example, Astemizole, Avanafil, Cisapride. The full list is on the Clarithromycin page.
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