Which cholinesterase inhibitor should be avoided in older adults whose syncope may be due to bradycardia?

• A. Donepezil
• B. Chlorpromazine
• C. Terazosin
• D. Amitriptyline

Answer: (A)

The key idea is that cholinesterase inhibitors raise acetylcholine levels, increasing parasympathetic (vagal) activity on the heart. That can slow the heart rate and slow conduction through the SA and AV nodes, which may lead to bradycardia and fainting (syncope). In an older adult whose syncope is likely due to bradycardia, a cholinesterase inhibitor would worsen the problem, so it should be avoided.

Donepezil is a cholinesterase inhibitor used for Alzheimer's disease, and it can cause bradycardia and syncope, making it the drug to avoid in this situation. The other options listed are not cholinesterase inhibitors; they have different primary actions (antipsychotic effects, alpha-1 blocking causing orthostatic hypotension, and antidepressant/anticholinergic effects) and do not pose the same bradycardia risk through increased acetylcholine.