Drug interactions
Nirmatrelvir / ritonavir + Quinidine
Severity: Contraindicated
Nirmatrelvir / ritonavir and Quinidine: contraindicated interaction.
Last updated
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 is a strong CYP3A4 inhibitor, and quinidine depends on CYP3A4 for clearance, so quinidine levels may rise sharply. This can cause serious ventricular arrhythmia and is contraindicated in labeling.
What this interaction means in plain words
Nirmatrelvir / ritonavir and Quinidine are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two.
Why it happens
Ritonavir inhibition of CYP3A4 metabolism of quinidine increases its exposure and QT risk.
What to do
Do not use together; consider an alternative COVID-19 therapy, or hold quinidine only on specialist advice.
What to ask your pharmacist
- Is there an alternative to one of these two medicines for me?
- If both are essential, who is monitoring me and how often?
- Which symptoms mean I should stop and seek help straight away?
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Other interactions of Quinidine
- Adagrasib + Quinidine Contraindicated
- Arsenic trioxide + Quinidine Contraindicated
- Artemether / lumefantrine + Quinidine Contraindicated
- Chloroquine + Quinidine Contraindicated
- Dofetilide + Quinidine Contraindicated
- Dronedarone + Quinidine Contraindicated
Frequently asked questions
Can I take Nirmatrelvir / ritonavir with Quinidine?
MediHelp rates the interaction as contraindicated. Nirmatrelvir / ritonavir and Quinidine are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two. Ritonavir is a strong CYP3A4 inhibitor, and quinidine depends on CYP3A4 for clearance, so quinidine levels may rise sharply. This can cause serious ventricular arrhythmia and is contraindicated in labeling.
How serious is the interaction between Nirmatrelvir / ritonavir and Quinidine?
MediHelp rates it contraindicated, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Do not use together; consider an alternative COVID-19 therapy, or hold quinidine only on specialist advice.
What other medicines interact with Quinidine?
MediHelp also lists interactions of Quinidine with, for example, Adagrasib, Arsenic trioxide, Artemether / lumefantrine. The full list is on the Quinidine page.
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