Clinical effects of high oral dose of donepezil for patients with Alzheimer's disease in Japan

Background:  Donepezil 10 mg/day gained approval in Japan in August 2007 for the treatment of cognitive dysfunction in advanced Alzheimer's disease. Methods:  We evaluated the efficacy and adverse effects of donepezil when the dose was increased to 10 mg/day in 61 Japanese patients with Alzheimer's disease. Cognitive function was evaluated using the Revised Hasegawa Dementia Scale and mini-mental state examination at the day before starting, and at 4, 8 and 24 weeks after starting donepezil 10 mg/day. The relationship with apolipoprotein E4 was also investigated. Results:  The Revised Hasegawa Dementia Scale and mini-mental state examination scores were not statistically significantly different at any time after starting donepezil 10 mg/day. It can be anticipated that donepezil 10 mg/day will especially inhibit deterioration of cognitive function in advanced Alzheimer's disease. The incidence of adverse events was 11.5%, lower than the rate of 40% or higher recorded during previous clinical trials. Conclusions:  The progression of cognitive dysfunction could be inhibited by increasing the dose of donepezil to 10 mg/day. It was suggested that longer-term treatment with 5 mg/day might lead to fewer adverse events when the dose is increased to 10 mg/day.