Drug interactions
Clarithromycin + Clozapine
Severity: Major
Clarithromycin and Clozapine: major interaction.
Last updated Sources: Health Canada product monograph
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
Clarithromycin can increase clozapine levels, raising the risk of sedation, seizures, hypotension and myocarditis-related effects. Both drugs also prolong the QT interval.
What this interaction means in plain words
Clarithromycin and Clozapine 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; Clozapine belongs to Central Nervous System.
Why it happens
Inhibition of CYP3A4 (and possibly CYP1A2) decreases clozapine clearance, plus additive QT prolongation.
What to do
Use an alternative antibiotic if possible. If unavoidable, monitor for clozapine toxicity and ECG, and consider checking clozapine levels and reducing the dose.
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 Clozapine
- Clozapine + Deferiprone Contraindicated
- Clozapine + Irinotecan Contraindicated
- Clozapine + Pimozide Contraindicated
- Clozapine + Thioridazine Contraindicated
- Acalabrutinib + Clozapine Major
- Adagrasib + Clozapine Major
Frequently asked questions
Can I take Clarithromycin with Clozapine?
MediHelp rates the interaction as major. Clarithromycin and Clozapine 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 can increase clozapine levels, raising the risk of sedation, seizures, hypotension and myocarditis-related effects. Both drugs also prolong the QT interval.
How serious is the interaction between Clarithromycin and Clozapine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use an alternative antibiotic if possible. If unavoidable, monitor for clozapine toxicity and ECG, and consider checking clozapine levels and reducing the dose.
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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