Drug interactions
Phenelzine + Promethazine
Severity: Moderate
Phenelzine 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
Phenelzine can intensify and prolong the anticholinergic and sedative effects of promethazine. This can result in excessive drowsiness, confusion, dry mouth, urinary retention and hypotension.
What this interaction means in plain words
Phenelzine 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.
Phenelzine belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Additive CNS depression and anticholinergic effects, with MAO inhibition potentially prolonging antihistamine effects.
What to do
Monitor for oversedation, anticholinergic toxicity and hypotension, and start with a reduced promethazine dose; choose a non-sedating antihistamine if suitable.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Phenelzine and Promethazine, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
Other interactions of Promethazine
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
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 Phenelzine with Promethazine?
MediHelp rates the interaction as moderate. Phenelzine 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. Phenelzine can intensify and prolong the anticholinergic and sedative effects of promethazine. This can result in excessive drowsiness, confusion, dry mouth, urinary retention and hypotension.
How serious is the interaction between Phenelzine 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 oversedation, anticholinergic toxicity and hypotension, and start with a reduced promethazine dose; choose a non-sedating antihistamine if suitable.
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.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
