Drug interactions
Methylene blue + Phenelzine
Severity: Contraindicated
Methylene blue and Phenelzine: contraindicated interaction.
Last updated Sources: UK 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 MAO-A and, when combined with serotonergic drugs, has caused serotonin syndrome. Phenelzine adds further MAO inhibition, increasing risk.
What this interaction means in plain words
Methylene blue and Phenelzine 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.
Why it happens
Methylene blue reversibly inhibits MAO-A, adding to phenelzine's MAO inhibition and raising serotonin levels.
What to do
Avoid unless methylene blue is needed for an emergency; then stop phenelzine and monitor for CNS toxicity. Resume the serotonergic drug 24 hours after the last methylene blue dose or after 2 weeks of monitoring, whichever comes first.
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
- Nardil 15 mg film-coated tablets - SmPC sections 4.3/4.5 (names the partner; "Methylthioninium chloride and 5HT3 antagonists should also be avoided.") — electronic medicines compendium (UK SmPC)
Other interactions of Phenelzine
- 5-HTP + Phenelzine Contraindicated
- Amitriptyline + Phenelzine Contraindicated
- Amoxapine + Phenelzine Contraindicated
- Atomoxetine + Phenelzine Contraindicated
- Benzphetamine + Phenelzine Contraindicated
- Brimonidine + Phenelzine Contraindicated
Frequently asked questions
Can I take Methylene blue with Phenelzine?
MediHelp rates the interaction as contraindicated. Methylene blue and Phenelzine 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. Methylene blue inhibits MAO-A and, when combined with serotonergic drugs, has caused serotonin syndrome. Phenelzine adds further MAO inhibition, increasing risk.
How serious is the interaction between Methylene blue and Phenelzine?
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 unless methylene blue is needed for an emergency; then stop phenelzine and monitor for CNS toxicity. Resume the serotonergic drug 24 hours after the last methylene blue dose or after 2 weeks of monitoring, whichever comes first.
What other medicines interact with Phenelzine?
MediHelp also lists interactions of Phenelzine with, for example, 5-HTP, Amitriptyline, Amoxapine. The full list is on the Phenelzine page.
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