Drug interactions
Dextromethorphan + Methylthioninium chloride
Severity: Major
Dextromethorphan and Methylthioninium chloride: 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
Dextromethorphan has serotonergic activity through serotonin reuptake inhibition, and methylthioninium chloride inhibits MAO-A. The combination can produce serotonin syndrome with agitation, hyperthermia, clonus and autonomic instability.
What this interaction means in plain words
Dextromethorphan and Methylthioninium chloride 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.
Dextromethorphan belongs to Respiratory; Methylthioninium chloride belongs to Miscellaneous.
Why it happens
MAO-A inhibition by methylthioninium combined with serotonin reuptake inhibition and release by dextromethorphan increases synaptic serotonin.
What to do
Avoid dextromethorphan-containing products during methylthioninium treatment and withhold them beforehand where feasible. Monitor for signs of serotonin toxicity if exposure occurs.
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 Methylthioninium chloride
Other interactions of Dextromethorphan
- Dextromethorphan + Isocarboxazid Contraindicated
- Dextromethorphan + Linezolid Contraindicated
- Dextromethorphan + Phenelzine Contraindicated
- Dextromethorphan + Rasagiline Contraindicated
- Dextromethorphan + Safinamide Contraindicated
- Dextromethorphan + Selegiline Contraindicated
Frequently asked questions
Can I take Dextromethorphan with Methylthioninium chloride?
MediHelp rates the interaction as major. Dextromethorphan and Methylthioninium chloride 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. Dextromethorphan has serotonergic activity through serotonin reuptake inhibition, and methylthioninium chloride inhibits MAO-A. The combination can produce serotonin syndrome with agitation, hyperthermia, clonus and autonomic instability.
How serious is the interaction between Dextromethorphan and Methylthioninium chloride?
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 dextromethorphan-containing products during methylthioninium treatment and withhold them beforehand where feasible. Monitor for signs of serotonin toxicity if exposure occurs.
What other medicines interact with Methylthioninium chloride?
MediHelp also lists interactions of Methylthioninium chloride with, for example, Levomilnacipran, Linezolid, Bupropion. The full list is on the Methylthioninium chloride page.
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