Drug interactions
Fluphenazine + Methadone
Severity: Major
Fluphenazine and Methadone: 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 cause sedation, so together they increase the risk of torsades de pointes, oversedation and respiratory depression. Methadone's serotonergic activity may rarely contribute to neuroleptic malignant-like or serotonin toxicity.
What this interaction means in plain words
Fluphenazine 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.
Fluphenazine belongs to Central Nervous System; Methadone belongs to Musculoskeletal.
Why it happens
Additive QT prolongation and CNS depression, with possible CYP2D6 competition.
What to do
Obtain a baseline ECG, monitor QTc and electrolytes, and use the lowest effective doses. Monitor for sedation, rigidity, hyperthermia and autonomic instability.
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 Fluphenazine
- Arsenic trioxide + Fluphenazine Contraindicated
- Dofetilide + Fluphenazine Contraindicated
- Fluphenazine + Ibutilide Contraindicated
- Fluphenazine + Pimozide Contraindicated
- Adagrasib + Fluphenazine Major
- Alfentanil + Fluphenazine Major
Frequently asked questions
Can I take Fluphenazine with Methadone?
MediHelp rates the interaction as major. Fluphenazine 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. Both drugs can prolong the QT interval and cause sedation, so together they increase the risk of torsades de pointes, oversedation and respiratory depression. Methadone's serotonergic activity may rarely contribute to neuroleptic malignant-like or serotonin toxicity.
How serious is the interaction between Fluphenazine 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: Obtain a baseline ECG, monitor QTc and electrolytes, and use the lowest effective doses. Monitor for sedation, rigidity, hyperthermia and autonomic instability.
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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