Efficacy of low-dose donepezil for visual hallucinations in a patient with dementia with Lewy bodies

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CHOLINESTERASE INHIBITORS (CHEI) are recommended for cognitive decline and behavioral and psychological symptoms of dementia in patients with dementia with Lewy bodies (DLB).1 We present a case relating the efficacy of low-dose donepezil for DLB. The patient was a 74-year-old Japanese woman who showed cognitive decline, visual hallucinations, and delusions over one year. She was previously treated with 1.5 mg/day of haloperidol, 1 mg/day of risperidone and 3–5 mg/day of donepezil. However, she developed parkinsonism with these drugs and the regime was stopped. Subsequently, the visual hallucinations and delusions disappeared without any psychotropic medication. Four months thereafter, visual hallucinations of small animals and delusions of persecution recurred and she was admitted to our medical center. She demonstrated no specific neurological findings including parkinsonism and her score for the mini-mental state examination was 24/30. Initially, she was suspected as having Alzheimer's disease (AD) and was administered 0.5 mg/day of risperidone and low-dose haloperidol (0.50–0.75 mg/day) for the visual hallucinations and delusions, but she developed significant parkinsonism including arm rigidity and stooped posture. Because she revealed fluctuating cognitive decline and severe neuroleptic sensitivity as well as visual hallucinations, her diagnosis was changed to probable DLB according to the clinical criteria for the diagnosis of DLB.1 Instead of these drugs, 3 mg/day of donepezil was effective for the visual hallucinations, but parkinsonism appeared. Next, the dose was decreased to 1.5 mg/day and parkinsonism disappeared without recurrence of the visual hallucinations. However, the delusions and fluctuating cognitive decline continued. Therefore, donepezil was stopped temporarily to determine whether the visual hallucinations actually improved due to the low-dose donepezil. Subsequently, the visual hallucinations reappeared, however they disappeared again with the re-administration of 1.5 mg/day of donepezil. Therefore, the efficacy of low-dose donepezil was confirmed. No randomized controlled trials have been carried out concerning the efficacy and dosage of donepezil for DLB patients, so the sensitivity of donepezil for its efficacy remains unclear. However, according to a previous report, adverse events due to donepezil occur more often in DLB patients than AD patients.2 The guidelines indicated that a dose-dependent exacerbation of extrapyramidal symptom (EPS) may occur with the administration of CHEI.1 The EPS of a DLB patient worsens with the therapeutic dose of rivastigmine (7.5 mg/day), which could be reversed by a dose reduction to 6 mg/day.3 In the current case, a dose-reduction of donepezil to 1.5 mg/day reversed the EPS. Therefore, titration to a low-dose treatment of donepezil might be useful in some DLB patients who show hypersensitivity to the standard dose of donepezil.

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