Drug interactions
Dextromethorphan + Methylene blue
Severity: Major
Dextromethorphan and Methylene blue: major interaction.
Last updated Sources: EMA SmPC
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
Methylene blue inhibits monoamine oxidase A and can cause serotonin syndrome when combined with serotonergic drugs such as dextromethorphan. Serious central nervous system toxicity has been reported with serotonergic agents given with methylene blue.
What this interaction means in plain words
Dextromethorphan and Methylene blue 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.
Why it happens
MAO-A inhibition by methylene blue increases serotonin, adding to the serotonergic effects of dextromethorphan.
What to do
Avoid the combination; if methylene blue is urgently needed, stop dextromethorphan and monitor for serotonin toxicity. Do not restart it until at least 24 hours after the last methylene blue dose.
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 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 Methylene blue?
MediHelp rates the interaction as major. Dextromethorphan and Methylene blue 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. Methylene blue inhibits monoamine oxidase A and can cause serotonin syndrome when combined with serotonergic drugs such as dextromethorphan. Serious central nervous system toxicity has been reported with serotonergic agents given with methylene blue.
How serious is the interaction between Dextromethorphan and Methylene blue?
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 the combination; if methylene blue is urgently needed, stop dextromethorphan and monitor for serotonin toxicity. Do not restart it until at least 24 hours after the last methylene blue dose.
What other medicines interact with Dextromethorphan?
MediHelp also lists interactions of Dextromethorphan with, for example, Isocarboxazid, Linezolid, Phenelzine. The full list is on the Dextromethorphan page.
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