Drug interactions
Doxylamine + Promethazine
Severity: Moderate
Doxylamine 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
Doxylamine is a strongly sedating antihistamine with anticholinergic effects, and promethazine has similar properties. Together they cause excessive sedation, confusion, dry mouth and urinary retention, and impaired next-day function.
What this interaction means in plain words
Doxylamine 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.
Doxylamine belongs to Respiratory; Promethazine belongs to Respiratory.
Why it happens
Additive H1 antagonism and muscarinic blockade.
What to do
Avoid combining two sedating antihistamines; use only one agent. Monitor older patients closely for confusion and falls if both are used.
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 Doxylamine 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
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
Other interactions of Doxylamine
Frequently asked questions
Can I take Doxylamine with Promethazine?
MediHelp rates the interaction as moderate. Doxylamine 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. Doxylamine is a strongly sedating antihistamine with anticholinergic effects, and promethazine has similar properties. Together they cause excessive sedation, confusion, dry mouth and urinary retention, and impaired next-day function.
How serious is the interaction between Doxylamine 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: Avoid combining two sedating antihistamines; use only one agent. Monitor older patients closely for confusion and falls if both are used.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Cabergoline, Dopamine, Ibutilide. 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.
