Drug interactions
Formoterol + Foscarnet
Severity: Major
Formoterol and Foscarnet: 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
Foscarnet can cause QT prolongation and also frequently causes hypokalemia, hypomagnesemia and hypocalcemia. Formoterol can further lower potassium and affect QTc, so the combination increases the risk of torsades de pointes.
What this interaction means in plain words
Formoterol and Foscarnet 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.
Formoterol belongs to Respiratory; Foscarnet belongs to Anti Virals.
Why it happens
Additive QT prolongation with foscarnet-induced electrolyte depletion and beta2-agonist-induced hypokalemia.
What to do
Monitor potassium, magnesium and calcium and replace deficits before and during foscarnet; obtain an ECG in patients with cardiac risk factors.
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 Formoterol
- Adagrasib + Formoterol Major
- Amiodarone + Formoterol Major
- Amisulpride + Formoterol Major
- Amitriptyline + Formoterol Major
- Amoxapine + Formoterol Major
- Arformoterol + Formoterol 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 Formoterol with Foscarnet?
MediHelp rates the interaction as major. Formoterol and Foscarnet 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 can cause QT prolongation and also frequently causes hypokalemia, hypomagnesemia and hypocalcemia. Formoterol can further lower potassium and affect QTc, so the combination increases the risk of torsades de pointes.
How serious is the interaction between Formoterol and Foscarnet?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor potassium, magnesium and calcium and replace deficits before and during foscarnet; obtain an ECG in patients with cardiac risk factors.
What other medicines interact with Formoterol?
MediHelp also lists interactions of Formoterol with, for example, Adagrasib, Amiodarone, Amisulpride. The full list is on the Formoterol page.
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