Drug interactions
Dimenhydrinate + Promethazine
Severity: Moderate
Dimenhydrinate 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
Dimenhydrinate contains diphenhydramine, a sedating antihistamine, and combining it with promethazine duplicates antihistamine and anticholinergic effects. This produces excessive drowsiness, confusion, dry mouth and urinary retention, especially in elderly patients.
What this interaction means in plain words
Dimenhydrinate 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.
Dimenhydrinate belongs to Respiratory; Promethazine belongs to Respiratory.
Why it happens
Additive H1 antagonism and muscarinic blockade.
What to do
Avoid concurrent use of both agents; choose one for nausea or vertigo. If unavoidable, monitor for oversedation and anticholinergic effects.
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
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
Other interactions of Dimenhydrinate
Frequently asked questions
Can I take Dimenhydrinate with Promethazine?
MediHelp rates the interaction as moderate. Dimenhydrinate 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. Dimenhydrinate contains diphenhydramine, a sedating antihistamine, and combining it with promethazine duplicates antihistamine and anticholinergic effects. This produces excessive drowsiness, confusion, dry mouth and urinary retention, especially in elderly patients.
How serious is the interaction between Dimenhydrinate 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 concurrent use of both agents; choose one for nausea or vertigo. If unavoidable, monitor for oversedation and anticholinergic effects.
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.
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