Compare the Efficacy and Safety of Donepezil Hydrochloride 23 mg Treatment With Continuation of Donepezil Hydrochloride 10 mg Treatment in Japanese Subjects With Severe Alzheimer's Disease

"Subjects in the Group-10 mg:~Week 1 to 4: Once daily donepezil 10 mg and placebo matching donepezil 5 mg, Week 5 to 28: Once daily donepezil 10 mg and placebo matching donepezil 23 mg, Week 29 to 32: Once daily donepezil 5 mg, 10 mg and placebo matching donepezil 23 mg, Week 33 to 52: Once daily donepezil 23 mg"

"Subjects in the Group-23 mg:~Week 1 to 4: Once daily donepezil 5 mg and 10 mg, Week 5 to 28: Once daily donepezil 23 mg and placebo matching donepezil 10 mg, Week 29 to 32: Once daily donepezil 23 mg, and placebo matching donepezil 5 mg and 10 mg, Week 33 to 52: Once daily donepezil 23 mg"