Drug interactions
Foscarnet + Procainamide
Severity: Major
Foscarnet and Procainamide: 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
Procainamide is a class Ia antiarrhythmic that prolongs QRS and QT intervals and can cause torsade de pointes. Foscarnet adds QT liability and electrolyte depletion, which increases the risk of serious ventricular arrhythmia.
What this interaction means in plain words
Foscarnet and Procainamide 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
Additive QT prolongation, with foscarnet-induced electrolyte depletion potentiating procainamide proarrhythmia.
What to do
Avoid the combination where possible and consider a non-QT-prolonging antiarrhythmic. If used together, monitor ECG and electrolytes closely and check procainamide levels.
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 Foscarnet
- Cidofovir + Foscarnet Contraindicated
- Foscarnet + Pimozide Contraindicated
- Foscarnet + Thioridazine Contraindicated
- Foscarnet + Vandetanib Contraindicated
- Adagrasib + Foscarnet Major
- Adefovir + Foscarnet Major
Frequently asked questions
Can I take Foscarnet with Procainamide?
MediHelp rates the interaction as major. Foscarnet and Procainamide 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. Procainamide is a class Ia antiarrhythmic that prolongs QRS and QT intervals and can cause torsade de pointes. Foscarnet adds QT liability and electrolyte depletion, which increases the risk of serious ventricular arrhythmia.
How serious is the interaction between Foscarnet and Procainamide?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination where possible and consider a non-QT-prolonging antiarrhythmic. If used together, monitor ECG and electrolytes closely and check procainamide levels.
What other medicines interact with Foscarnet?
MediHelp also lists interactions of Foscarnet with, for example, Cidofovir, Pimozide, Thioridazine. The full list is on the Foscarnet page.
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