Drug interactions
Clarithromycin + Posaconazole
Severity: Major
Clarithromycin and Posaconazole: major interaction.
Last updated Sources: UK SmPC
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 can prolong the QT interval, increasing the risk of torsades de pointes. Clarithromycin may also increase posaconazole exposure, and posaconazole inhibits CYP3A4, raising clarithromycin levels.
What this interaction means in plain words
Clarithromycin and Posaconazole 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; Posaconazole belongs to Anti Fungals.
Why it happens
Additive QT prolongation, with mutual pharmacokinetic effects via CYP3A4 and P-glycoprotein.
What to do
Avoid combining if an alternative antibiotic exists. If required, obtain baseline ECG, correct electrolytes and monitor 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 Posaconazole
- Artemether + Posaconazole Contraindicated
- Avanafil + Posaconazole Contraindicated
- Cobimetinib + Posaconazole Contraindicated
- Conivaptan + Posaconazole Contraindicated
- Dihydroergotamine intranasal + Posaconazole Contraindicated
- Dihydroergotamine + Posaconazole Contraindicated
Frequently asked questions
Can I take Clarithromycin with Posaconazole?
MediHelp rates the interaction as major. Clarithromycin and Posaconazole 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 can prolong the QT interval, increasing the risk of torsades de pointes. Clarithromycin may also increase posaconazole exposure, and posaconazole inhibits CYP3A4, raising clarithromycin levels.
How serious is the interaction between Clarithromycin and Posaconazole?
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 combining if an alternative antibiotic exists. If required, obtain baseline ECG, correct electrolytes and monitor 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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