Drug interactions
Foscarnet + Methadone
Severity: Major
Foscarnet and Methadone: major 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 hypocalcemia, hypomagnesemia and hypokalemia. With methadone this raises the risk of torsades de pointes.
What this interaction means in plain words
Foscarnet and Methadone 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; Methadone belongs to Musculoskeletal.
Why it happens
Additive QT prolongation, worsened by foscarnet-induced electrolyte depletion.
What to do
Monitor ECG and serum calcium, magnesium and potassium during foscarnet infusions, correcting abnormalities promptly. Consider reducing the methadone dose or an alternative antiviral if QTc rises significantly.
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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Other interactions of Methadone
- Alvimopan + Methadone Contraindicated
- Calcium / magnesium / potassium / sodium oxybates + Methadone Contraindicated
- Droperidol + Methadone Contraindicated
- Ibutilide + Methadone Contraindicated
- Isocarboxazid + Methadone Contraindicated
- Lefamulin + Methadone Contraindicated
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 Methadone?
MediHelp rates the interaction as major. Foscarnet and Methadone 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 prolong the QT interval and cause electrolyte disturbances such as hypocalcemia, hypomagnesemia and hypokalemia. With methadone this raises the risk of torsades de pointes.
How serious is the interaction between Foscarnet and Methadone?
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 ECG and serum calcium, magnesium and potassium during foscarnet infusions, correcting abnormalities promptly. Consider reducing the methadone dose or an alternative antiviral if QTc rises significantly.
What other medicines interact with Methadone?
MediHelp also lists interactions of Methadone with, for example, Alvimopan, Calcium / magnesium / potassium / sodium oxybates, Droperidol. The full list is on the Methadone page.
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