Drug interactions
Letermovir + Quinidine
Severity: Moderate
Letermovir and Quinidine: moderate 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
Letermovir is a moderate CYP3A4 inhibitor and may raise quinidine plasma concentrations. Higher quinidine exposure increases the risk of QT prolongation and ventricular arrhythmias, especially given quinidine's narrow therapeutic index.
What this interaction means in plain words
Letermovir and Quinidine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Letermovir belongs to Anti Virals; Quinidine belongs to Anti Parasitic.
Why it happens
Letermovir inhibits CYP3A4-mediated metabolism of quinidine, reducing its clearance.
What to do
Monitor ECG (QTc) and quinidine serum concentrations when starting or stopping letermovir. Reduce the quinidine dose if QTc prolongation or toxicity appears.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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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
Other interactions of Letermovir
- Ergotamine + Letermovir Contraindicated
- Letermovir + Pimozide Contraindicated
- Apalutamide + Letermovir Major
- Atorvastatin + Letermovir Major
- Carbamazepine + Letermovir Major
- Colchicine + Letermovir Major
Frequently asked questions
Can I take Letermovir with Quinidine?
MediHelp rates the interaction as moderate. Letermovir and Quinidine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Letermovir is a moderate CYP3A4 inhibitor and may raise quinidine plasma concentrations. Higher quinidine exposure increases the risk of QT prolongation and ventricular arrhythmias, especially given quinidine's narrow therapeutic index.
How serious is the interaction between Letermovir and Quinidine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor ECG (QTc) and quinidine serum concentrations when starting or stopping letermovir. Reduce the quinidine dose if QTc prolongation or toxicity appears.
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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