Drug interactions
Diphenhydramine + Memantine-donepezil
Severity: Moderate
Diphenhydramine and Memantine-donepezil: 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
Diphenhydramine has strong anticholinergic effects that oppose donepezil and can worsen cognition and confusion in older patients. It is also sedating and a CYP2D6 inhibitor.
What this interaction means in plain words
Diphenhydramine and Memantine-donepezil 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.
Diphenhydramine belongs to Respiratory; Memantine-donepezil belongs to Central Nervous System.
Why it happens
Pharmacodynamic antagonism between muscarinic blockade and cholinesterase inhibition.
What to do
Avoid diphenhydramine in patients with dementia and use a non-sedating second-generation antihistamine such as loratadine instead.
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 Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Memantine-donepezil?
MediHelp rates the interaction as moderate. Diphenhydramine and Memantine-donepezil 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. Diphenhydramine has strong anticholinergic effects that oppose donepezil and can worsen cognition and confusion in older patients. It is also sedating and a CYP2D6 inhibitor.
How serious is the interaction between Diphenhydramine and Memantine-donepezil?
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 diphenhydramine in patients with dementia and use a non-sedating second-generation antihistamine such as loratadine instead.
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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