Syncope secondary to second-degree atrioventricular block with donepezil use.

Donepezil, an acetylcholinesterase inhibitor, is approved for the treatment of mild to moderate dementia secondary to Alzheimer's disease. Although most prescribers are aware of the common gastrointestinal side effects of donepezil, cardiovascular side effects are rarely observed. Cardiovascular side effects of donepezil have almost always been observed in patients with a history of conduction defects or sick sinus syndrome. We report a case of a woman with early onset Alzheimer's disease and no history of cardiac disease who developed second-degree heart block after a few weeks of therapy with donepezil. Withdrawal of donepezil led to resolution of the atrioventricular block.