Drug interactions
Fluvoxamine + Methadone
Severity: Major
Fluvoxamine 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
Fluvoxamine inhibits CYP1A2, CYP2C19 and CYP3A4 and can substantially raise methadone concentrations, leading to sedation, respiratory depression and QT prolongation. Both drugs may also prolong the QT interval and carry serotonergic potential.
What this interaction means in plain words
Fluvoxamine 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.
Fluvoxamine belongs to Central Nervous System; Methadone belongs to Musculoskeletal.
Why it happens
Fluvoxamine inhibits CYP-mediated methadone metabolism, with additive QT prolongation.
What to do
Monitor for opioid toxicity and QTc when fluvoxamine is started or stopped, and reduce the methadone dose if needed. Consider an SSRI with less CYP inhibition.
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 Fluvoxamine
- Agomelatine + Fluvoxamine Contraindicated
- Alosetron + Fluvoxamine Contraindicated
- Fezolinetant + Fluvoxamine Contraindicated
- Fluvoxamine + Isocarboxazid Contraindicated
- Fluvoxamine + Mavacamten Contraindicated
- Fluvoxamine + Methylene blue Contraindicated
Frequently asked questions
Can I take Fluvoxamine with Methadone?
MediHelp rates the interaction as major. Fluvoxamine 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. Fluvoxamine inhibits CYP1A2, CYP2C19 and CYP3A4 and can substantially raise methadone concentrations, leading to sedation, respiratory depression and QT prolongation. Both drugs may also prolong the QT interval and carry serotonergic potential.
How serious is the interaction between Fluvoxamine 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 for opioid toxicity and QTc when fluvoxamine is started or stopped, and reduce the methadone dose if needed. Consider an SSRI with less CYP inhibition.
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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