Drug interactions
Foscarnet + Pentamidine
Severity: Major
Foscarnet and Pentamidine: 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
Both drugs can prolong the QT interval, and each is also associated with electrolyte disturbances such as hypocalcemia, hypomagnesemia or hypokalemia. They also share nephrotoxic potential, which can worsen electrolyte handling. The combination substantially increases the risk of torsade de pointes.
What this interaction means in plain words
Foscarnet and Pentamidine 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.
Foscarnet belongs to Anti Virals; Pentamidine belongs to Anti Parasitic.
Why it happens
Additive QT prolongation and electrolyte disturbance, with overlapping nephrotoxicity.
What to do
Avoid concurrent use where an alternative exists. If both are essential, monitor ECG, renal function and electrolytes frequently and replace deficits promptly.
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
Other interactions of Pentamidine
- Clomipramine + Pentamidine Contraindicated
- Desipramine + Pentamidine Contraindicated
- Dronedarone + Pentamidine Contraindicated
- Moxifloxacin + Pentamidine Contraindicated
- Nortriptyline + Pentamidine Contraindicated
- Pentamidine + Pimozide Contraindicated
Frequently asked questions
Can I take Foscarnet with Pentamidine?
MediHelp rates the interaction as major. Foscarnet and Pentamidine 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. Both drugs can prolong the QT interval, and each is also associated with electrolyte disturbances such as hypocalcemia, hypomagnesemia or hypokalemia. They also share nephrotoxic potential, which can worsen electrolyte handling. The combination substantially increases the risk of torsade de pointes.
How serious is the interaction between Foscarnet and Pentamidine?
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 concurrent use where an alternative exists. If both are essential, monitor ECG, renal function and electrolytes frequently and replace deficits promptly.
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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