The most common side effects of cholinesterase inhibitors are procholinergic (opposite of anticholinergic) include:
At lower doses: GI side effects (nausea, diarrhea, vomiting), weight loss, decreased appetite, insomnia, fatigue, muscle cramps, myalgia
Can cause dizziness, drowsiness, or syncope, especially during initiation of therapy
Discontinue if bradycardia develops or there is a significant conduction abnormality (i.e. - more than a first degree heart block)
At higher doses: side effects include headaches, dizziness, drowsiness, blurred vision, urinary frequency and incontinence
Can aggravate asthma and other breathing problems, and increase risk of seizures
Night-time administration of donepezil can cause night-time disturbances, including insomnia, nightmares, and vivid dreams.