Drug interactions
Methylene blue + Promethazine
Severity: Moderate
Methylene blue and Promethazine: moderate 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
Methylene blue is a potent reversible MAO-A inhibitor and can cause serotonin syndrome with serotonergic drugs. Promethazine has only weak, uncertain serotonergic activity, so the risk is probably low, but it also causes additive sedation and has been listed as a precaution. Severe reactions have been reported mainly with SSRIs and similar agents.
What this interaction means in plain words
Methylene blue and Promethazine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
MAO-A inhibition by methylene blue may increase serotonin, while promethazine contributes only uncertain serotonergic effects.
What to do
Monitor for agitation, tremor, hyperthermia, clonus and autonomic instability after methylene blue is given. Prefer a non-serotonergic alternative where possible.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Promethazine
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
Frequently asked questions
Can I take Methylene blue with Promethazine?
MediHelp rates the interaction as moderate. Methylene blue and Promethazine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Methylene blue is a potent reversible MAO-A inhibitor and can cause serotonin syndrome with serotonergic drugs. Promethazine has only weak, uncertain serotonergic activity, so the risk is probably low, but it also causes additive sedation and has been listed as a precaution. Severe reactions have been reported mainly with SSRIs and similar agents.
How serious is the interaction between Methylene blue and Promethazine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for agitation, tremor, hyperthermia, clonus and autonomic instability after methylene blue is given. Prefer a non-serotonergic alternative where possible.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Ibutilide, Pimozide, Thioridazine. The full list is on the Promethazine page.
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