Drug interactions
Foscarnet + Promethazine
Severity: Moderate
Foscarnet and Promethazine: 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
Foscarnet can prolong the QT interval and cause electrolyte disturbances such as low calcium, magnesium and potassium, which increase arrhythmia risk. Adding promethazine may further increase the risk of torsades de pointes.
What this interaction means in plain words
Foscarnet and Promethazine 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.
Foscarnet belongs to Anti Virals; Promethazine belongs to Respiratory.
Why it happens
Additive QT prolongation, amplified by foscarnet-induced electrolyte disturbances.
What to do
Monitor ECG and serum electrolytes including calcium and magnesium, and correct abnormalities; consider a non-QT-prolonging alternative.
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 Promethazine
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
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 Promethazine?
MediHelp rates the interaction as moderate. Foscarnet and Promethazine 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. Foscarnet can prolong the QT interval and cause electrolyte disturbances such as low calcium, magnesium and potassium, which increase arrhythmia risk. Adding promethazine may further increase the risk of torsades de pointes.
How serious is the interaction between Foscarnet and Promethazine?
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 and serum electrolytes including calcium and magnesium, and correct abnormalities; consider a non-QT-prolonging alternative.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Cabergoline, Dopamine, Ibutilide. The full list is on the Promethazine page.
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