Drug interactions
Diltiazem + Nirmatrelvir / ritonavir
Severity: Major
Diltiazem and Nirmatrelvir / ritonavir: 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
Ritonavir strongly inhibits CYP3A4 and can substantially increase diltiazem exposure. This may cause bradycardia, hypotension, AV block and heart failure exacerbation.
What this interaction means in plain words
Diltiazem and Nirmatrelvir / ritonavir 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.
Why it happens
Ritonavir-mediated inhibition of CYP3A4 reduces diltiazem clearance.
What to do
Consider reducing the diltiazem dose and monitor heart rate, blood pressure and ECG during treatment and for a few days afterward. Use an alternative antiviral if the patient cannot be monitored.
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 Diltiazem
- Diltiazem + Flibanserin Contraindicated
- Diltiazem + Ivabradine Contraindicated
- Diltiazem + Lomitapide Contraindicated
- Diltiazem + Lonafarnib Contraindicated
- Acebutolol + Diltiazem Major
- Alfentanil + Diltiazem Major
Frequently asked questions
Can I take Diltiazem with Nirmatrelvir / ritonavir?
MediHelp rates the interaction as major. Diltiazem and Nirmatrelvir / ritonavir 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. Ritonavir strongly inhibits CYP3A4 and can substantially increase diltiazem exposure. This may cause bradycardia, hypotension, AV block and heart failure exacerbation.
How serious is the interaction between Diltiazem and Nirmatrelvir / ritonavir?
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 diltiazem dose and monitor heart rate, blood pressure and ECG during treatment and for a few days afterward. Use an alternative antiviral if the patient cannot be monitored.
What other medicines interact with Diltiazem?
MediHelp also lists interactions of Diltiazem with, for example, Flibanserin, Ivabradine, Lomitapide. The full list is on the Diltiazem page.
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