Drug interactions
Memantine-donepezil + Promethazine
Severity: Moderate
Memantine-donepezil 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 is strongly anticholinergic and can oppose donepezil's cholinergic action while worsening confusion in dementia. It also has a modest QT-prolonging potential that may add to that of donepezil.
What this interaction means in plain words
Memantine-donepezil 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.
Memantine-donepezil belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Pharmacodynamic antagonism at muscarinic receptors with possible additive QT prolongation.
What to do
Avoid promethazine in patients with dementia where possible and choose a non-sedating, non-anticholinergic alternative. If used, monitor cognition and sedation.
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 Memantine-donepezil
- Dronedarone + Memantine-donepezil Contraindicated
- Memantine-donepezil + Thioridazine Contraindicated
- Amantadine + Memantine-donepezil Major
- Amiodarone + Memantine-donepezil Major
- Amisulpride + Memantine-donepezil Major
- Amitriptyline + Memantine-donepezil Major
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 Memantine-donepezil with Promethazine?
MediHelp rates the interaction as moderate. Memantine-donepezil 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 is strongly anticholinergic and can oppose donepezil's cholinergic action while worsening confusion in dementia. It also has a modest QT-prolonging potential that may add to that of donepezil.
How serious is the interaction between Memantine-donepezil 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-sedating, non-anticholinergic alternative. If used, monitor cognition and sedation.
What other medicines interact with Memantine-donepezil?
MediHelp also lists interactions of Memantine-donepezil with, for example, Dronedarone, Thioridazine, Amantadine. The full list is on the Memantine-donepezil page.
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