A 72-year old lady, known case of Alzheimer's disease (AD), with Dementia with Behavioral Disturbance (DBD) and Parkinson's Disease (PD), had erroneously received 43 mg/day of donepezil for 7 days instead of her regular dosage of 20mg/day. She presented with rapid-onset global rigidity and subsequent altered sensorium. She was diagnosed with Metabolic Encephalopathy and acute exacerbation of PD in a known case of AD, DBD and PD. MRI brain revealed no acute changes. She was monitored in ICU

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... p, given supportive and symptomatic treatment; her anti-parkinsonian regime was stepped up and she recovered completely in 14 days. As per literature, as no other attribution for the rigidity was plausible after an extensive neuro-psychiatric investigation, this is postulated to be a rare presentation of acute exacerbation of PD brought on by excessive doses of donepezil in an existing case of dementia with PD.