[Abnormal posture of the trunk related to donepezil hydrochloride: report of 2 cases].

Patient 1, an 80-year-old woman with Alzheimer's disease, had been taking donepezil 5 mg for 2 years. Donepezil was increased to 10 mg, and 2 months later, the patient developed dropped head syndrome. MRI and needle EMG abnormality of the neck extensor muscles suggested focal myopathy, but the symptom disappeared within 2 months by discontinuing donepezil. Patient 2, a 78-year-old man with Lewy body dementia, had been taking levodopa and pramipexole (PPX). One month after tapering levodopa, donepezil 3 mg was introduced, and Pisa syndrome (bending of the trunk to the right anterior direction) developed 10 days later. Donepezil and PPX were discontinued and levodopa was increased. Within 5 months, his posture had almost recovered. Cholinesterase inhibitors can induce abnormal posture of the trunk, and clinicians should be aware of this uncommon but important side effect.