Drug interactions
Donepezil + Trihexyphenidyl
Severity: Moderate
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
Donepezil enhances cholinergic transmission while trihexyphenidyl blocks it, so the drugs oppose each other. Cognitive benefit from donepezil may be reduced, and donepezil may worsen or complicate parkinsonian symptom control.
What this interaction means in plain words
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.
Donepezil belongs to Central Nervous System; Trihexyphenidyl belongs to Central Nervous System.
Why it happens
Pharmacodynamic antagonism between a cholinesterase inhibitor and a muscarinic antagonist.
What to do
Avoid combining where possible and reassess the need for the anticholinergic in dementia. If both are used, monitor cognition and motor symptoms and keep the trihexyphenidyl dose low.
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 Trihexyphenidyl
Other interactions of Donepezil
- Donepezil + Dronedarone Contraindicated
- Donepezil + Pimozide Contraindicated
- Donepezil + Thioridazine Contraindicated
- Donepezil + Vandetanib Contraindicated
- Amiodarone + Donepezil Major
- Amisulpride + Donepezil Major
Frequently asked questions
Can I take Donepezil with Trihexyphenidyl?
MediHelp rates the interaction as moderate. 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. Donepezil enhances cholinergic transmission while trihexyphenidyl blocks it, so the drugs oppose each other. Cognitive benefit from donepezil may be reduced, and donepezil may worsen or complicate parkinsonian symptom control.
How serious is the interaction between 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 where possible and reassess the need for the anticholinergic in dementia. If both are used, monitor cognition and motor symptoms and keep the trihexyphenidyl dose low.
What other medicines interact with Trihexyphenidyl?
MediHelp also lists interactions of Trihexyphenidyl with, for example, Orphenadrin, Oxybutynin, Scopolamine. The full list is on the Trihexyphenidyl page.
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