Drug interactions
Clarithromycin + Phenytoin
Severity: Moderate
Clarithromycin and Phenytoin: 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
Phenytoin induces CYP3A4 and may lower clarithromycin concentrations, risking reduced efficacy. Clarithromycin may also raise phenytoin levels, so the interaction can act in both directions.
What this interaction means in plain words
Clarithromycin and Phenytoin 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.
Clarithromycin belongs to Anti Bacterial; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4, increasing clarithromycin clearance, while clarithromycin may inhibit phenytoin metabolism.
What to do
Monitor phenytoin concentrations and for signs of toxicity such as nystagmus or ataxia, and assess clinical response to clarithromycin. Consider an alternative antibiotic such as azithromycin if needed.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Clarithromycin and Phenytoin, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
Other interactions of Clarithromycin
- Astemizole + Clarithromycin Contraindicated
- Avanafil + Clarithromycin Contraindicated
- Cisapride + Clarithromycin Contraindicated
- Clarithromycin + Colchicine Contraindicated
- Clarithromycin + Conivaptan Contraindicated
- Clarithromycin + Dihydroergotamine Contraindicated
Other interactions of Phenytoin
- Artemether / lumefantrine + Phenytoin Contraindicated
- Bictegravir + Phenytoin Contraindicated
- Cabotegravir + Phenytoin Contraindicated
- Doravirine + Phenytoin Contraindicated
- Elbasvir / grazoprevir + Phenytoin Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Phenytoin Contraindicated
Frequently asked questions
Can I take Clarithromycin with Phenytoin?
MediHelp rates the interaction as moderate. Clarithromycin and Phenytoin 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. Phenytoin induces CYP3A4 and may lower clarithromycin concentrations, risking reduced efficacy. Clarithromycin may also raise phenytoin levels, so the interaction can act in both directions.
How serious is the interaction between Clarithromycin and Phenytoin?
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 phenytoin concentrations and for signs of toxicity such as nystagmus or ataxia, and assess clinical response to clarithromycin. Consider an alternative antibiotic such as azithromycin if needed.
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.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
