Drug interactions
Methadone + Thioridazine
Severity: Contraindicated
Methadone and Thioridazine: contraindicated 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 prolong the QT interval, and thioridazine is notably associated with torsades de pointes and sudden cardiac death. Their combination also increases sedation and CNS depression. Thioridazine labeling contraindicates use with other drugs that prolong the QTc.
What this interaction means in plain words
Methadone and Thioridazine are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two.
Methadone belongs to Musculoskeletal; Thioridazine belongs to Central Nervous System.
Why it happens
Additive QT prolongation through cardiac potassium channel blockade, plus additive CNS depression; thioridazine also inhibits CYP2D6, which may modestly affect methadone exposure.
What to do
Avoid the combination and choose an antipsychotic with lower QT liability. If it cannot be avoided, use continuous ECG and electrolyte monitoring under specialist supervision.
What to ask your pharmacist
- Is there an alternative to one of these two medicines for me?
- If both are essential, who is monitoring me and how often?
- Which symptoms mean I should stop and seek help straight away?
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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 Thioridazine
- Abiraterone + Thioridazine Contraindicated
- Adagrasib + Thioridazine Contraindicated
- Amiodarone + Thioridazine Contraindicated
- Amisulpride + Thioridazine Contraindicated
- Amitriptyline + Thioridazine Contraindicated
- Amoxapine + Thioridazine Contraindicated
Frequently asked questions
Can I take Methadone with Thioridazine?
MediHelp rates the interaction as contraindicated. Methadone and Thioridazine are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two. Both drugs prolong the QT interval, and thioridazine is notably associated with torsades de pointes and sudden cardiac death. Their combination also increases sedation and CNS depression. Thioridazine labeling contraindicates use with other drugs that prolong the QTc.
How serious is the interaction between Methadone and Thioridazine?
MediHelp rates it contraindicated, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination and choose an antipsychotic with lower QT liability. If it cannot be avoided, use continuous ECG and electrolyte monitoring under specialist supervision.
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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