Drug interactions
Clozapine + Nirmatrelvir
Severity: Major
Clozapine and Nirmatrelvir: 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
Nirmatrelvir is given with ritonavir, which strongly inhibits CYP3A4 and can raise clozapine concentrations, increasing the risk of sedation, hypotension, seizures and myocarditis. Clozapine is also affected by inflammation during infection, which further complicates levels.
What this interaction means in plain words
Clozapine and Nirmatrelvir 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.
Clozapine belongs to Central Nervous System; Nirmatrelvir belongs to Anti Virals.
Why it happens
Ritonavir-boosted CYP3A4 inhibition (and CYP1A2 effects) reduces clozapine clearance.
What to do
Consider reducing the clozapine dose during the five-day course and monitor for toxicity, or use an alternative antiviral. Check clozapine levels if available.
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 Clozapine
- Clozapine + Deferiprone Contraindicated
- Clozapine + Irinotecan Contraindicated
- Clozapine + Pimozide Contraindicated
- Clozapine + Thioridazine Contraindicated
- Acalabrutinib + Clozapine Major
- Adagrasib + Clozapine Major
Other interactions of Nirmatrelvir
- Alfuzosin + Nirmatrelvir Contraindicated
- Amiodarone + Nirmatrelvir Contraindicated
- Apalutamide + Nirmatrelvir Contraindicated
- Carbamazepine + Nirmatrelvir Contraindicated
- Colchicine + Nirmatrelvir Contraindicated
- Dronedarone + Nirmatrelvir Contraindicated
Frequently asked questions
Can I take Clozapine with Nirmatrelvir?
MediHelp rates the interaction as major. Clozapine and Nirmatrelvir 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. Nirmatrelvir is given with ritonavir, which strongly inhibits CYP3A4 and can raise clozapine concentrations, increasing the risk of sedation, hypotension, seizures and myocarditis. Clozapine is also affected by inflammation during infection, which further complicates levels.
How serious is the interaction between Clozapine and Nirmatrelvir?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Consider reducing the clozapine dose during the five-day course and monitor for toxicity, or use an alternative antiviral. Check clozapine levels if available.
What other medicines interact with Clozapine?
MediHelp also lists interactions of Clozapine with, for example, Deferiprone, Irinotecan, Pimozide. The full list is on the Clozapine page.
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