Drug interactions
Memantine-donepezil + Trihexyphenidyl
Severity: Moderate
Memantine-donepezil and Trihexyphenidyl: 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
Trihexyphenidyl is a centrally acting anticholinergic and opposes the cholinergic effect of donepezil. The result may be reduced efficacy of both drugs, and trihexyphenidyl can worsen cognition and confusion in dementia.
What this interaction means in plain words
Memantine-donepezil and Trihexyphenidyl 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; Trihexyphenidyl belongs to Central Nervous System.
Why it happens
Pharmacodynamic antagonism between muscarinic blockade and cholinesterase inhibition.
What to do
Avoid combining if an alternative for parkinsonism is available. If both are needed, use the lowest effective trihexyphenidyl dose and monitor cognition and motor symptoms.
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 Trihexyphenidyl
Frequently asked questions
Can I take Memantine-donepezil with Trihexyphenidyl?
MediHelp rates the interaction as moderate. Memantine-donepezil and Trihexyphenidyl 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. Trihexyphenidyl is a centrally acting anticholinergic and opposes the cholinergic effect of donepezil. The result may be reduced efficacy of both drugs, and trihexyphenidyl can worsen cognition and confusion in dementia.
How serious is the interaction between Memantine-donepezil and Trihexyphenidyl?
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 if an alternative for parkinsonism is available. If both are needed, use the lowest effective trihexyphenidyl dose and monitor cognition and motor symptoms.
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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