Study Goal. To assess and compare the effect of donepezil in the treatment of dementia in Parkinson’s disease (PD) and Alzheimer’s disease (AD). Methods. Seven patients with PD and dementia (PDD) and 7 patients with AD according to valid diagnostic criteria were followed up prospectively for 6 months. Both patient groups (AD and PDD) were comparable in age (72 ± 5 and 70 ± 8), gender, education and the entry average Mini-Mental State Examination (MMSE) score: 17.7 ± 5.1 in the AD group and 19.8 ± 3.2 in the PDD group. Patients were evaluated on entering the study and each 3 months using a standardized MMSE scale and in the PDD group also with the motor subscale of UPDRS III (Unified Parkinson’s Disease Rating Scale III: Motor Examination). Results. All patients finished the study. The average daily dose of donepezil at the end of the study was comparable in both groups (9.3 ± 1.8 in the AD group and 8.6 ± 2.3 in the PDD group). There was no significant between-visits or between-groups (AD and PDD) difference conceruing the mean MMSE scores; ANOVA: F(2,36) = 0.236, P = 0.79. The scores on UPDRS motor subscale at the beginning and end of the study did not differ either; t-test: P=0.86. Conclusion.The effect of donepezil was permanent and comparable inADandPDDfor a period of 6 months since the beginning of treatment. Donepezil was well tolerated in both groups, in the PDD group using daily therapeutic dose of 5–10 mg and with stable antiparkinsonian medication the symptoms of parkinsonism did not deteriorate.

        Key words: dementia, Parkinson’s disease, Alzheimer disease, donepezil