Drug interactions
Clarithromycin + Fluconazole
Severity: Major
Clarithromycin and Fluconazole: major interaction.
Last updated Sources: US FDA label
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
Both agents prolong the QT interval, and fluconazole also inhibits CYP3A4, which can raise clarithromycin concentrations. The combined effect increases the risk of torsades de pointes, especially with electrolyte disturbances or underlying heart disease.
What this interaction means in plain words
Clarithromycin and Fluconazole 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.
Clarithromycin belongs to Anti Bacterial; Fluconazole belongs to Anti Fungals.
Why it happens
Additive QT prolongation with fluconazole inhibition of CYP3A4 metabolism of clarithromycin.
What to do
Avoid the combination if an alternative antibiotic or antifungal is available. If both are required, check a baseline ECG, correct potassium and magnesium, and monitor the QTc.
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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References
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 Fluconazole
- Dihydroergotamine intranasal + Fluconazole Contraindicated
- Dihydroergotamine + Fluconazole Contraindicated
- Dofetilide + Fluconazole Contraindicated
- Domperidone + Fluconazole Contraindicated
- Dronedarone + Fluconazole Contraindicated
- Erythromycin + Fluconazole Contraindicated
Frequently asked questions
Can I take Clarithromycin with Fluconazole?
MediHelp rates the interaction as major. Clarithromycin and Fluconazole 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. Both agents prolong the QT interval, and fluconazole also inhibits CYP3A4, which can raise clarithromycin concentrations. The combined effect increases the risk of torsades de pointes, especially with electrolyte disturbances or underlying heart disease.
How serious is the interaction between Clarithromycin and Fluconazole?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination if an alternative antibiotic or antifungal is available. If both are required, check a baseline ECG, correct potassium and magnesium, and monitor the QTc.
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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