Drug interactions
Arsenic trioxide + Methadone
Severity: Major
Arsenic trioxide and Methadone: major interaction.
Last updated Sources: Health Canada product monograph
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
Arsenic trioxide causes marked QT prolongation and can provoke torsades de pointes; methadone also prolongs the QT interval. Combined use substantially raises the risk of serious ventricular arrhythmias.
What this interaction means in plain words
Arsenic trioxide 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.
Arsenic trioxide belongs to Oncology; Methadone belongs to Musculoskeletal.
Why it happens
Additive QT prolongation via cardiac repolarization effects.
What to do
Avoid if possible and consider a non-QT-prolonging opioid. If unavoidable, monitor ECG frequently and keep potassium and magnesium within normal range.
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 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 Arsenic trioxide
- Amiodarone + Arsenic trioxide Contraindicated
- Amisulpride + Arsenic trioxide Contraindicated
- Arsenic trioxide + Clomipramine Contraindicated
- Arsenic trioxide + Dronedarone Contraindicated
- Arsenic trioxide + Fluphenazine Contraindicated
- Arsenic trioxide + Gemifloxacin Contraindicated
Frequently asked questions
Can I take Arsenic trioxide with Methadone?
MediHelp rates the interaction as major. Arsenic trioxide 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. Arsenic trioxide causes marked QT prolongation and can provoke torsades de pointes; methadone also prolongs the QT interval. Combined use substantially raises the risk of serious ventricular arrhythmias.
How serious is the interaction between Arsenic trioxide 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: Avoid if possible and consider a non-QT-prolonging opioid. If unavoidable, monitor ECG frequently and keep potassium and magnesium within normal range.
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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