Drug interactions
Donepezil transdermal + Promethazine
Severity: Moderate
Donepezil transdermal 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
Promethazine has strong anticholinergic activity that opposes the cholinesterase-inhibiting effect of donepezil, potentially reducing cognitive benefit. Anticholinergics can also worsen confusion in patients with dementia.
What this interaction means in plain words
Donepezil transdermal 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
Pharmacodynamic antagonism between muscarinic receptor blockade and increased acetylcholine from cholinesterase inhibition.
What to do
Avoid promethazine in patients with dementia where possible and choose a non-anticholinergic antiemetic or antihistamine; monitor cognition if combined.
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
Frequently asked questions
Can I take Donepezil transdermal with Promethazine?
MediHelp rates the interaction as moderate. Donepezil transdermal 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. Promethazine has strong anticholinergic activity that opposes the cholinesterase-inhibiting effect of donepezil, potentially reducing cognitive benefit. Anticholinergics can also worsen confusion in patients with dementia.
How serious is the interaction between Donepezil transdermal 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 promethazine in patients with dementia where possible and choose a non-anticholinergic antiemetic or antihistamine; monitor cognition if combined.
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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