BACKGROUND: Cholinergic deficits are prominent in patients who have dementia associated with Parkinson s disease. We investigated the effects of the dual c holinesterase inhibitor rivastigmine in such patients. METHODS: Patients in whom mild to moderate dementia developed at least 2 years after they received a clinical diagnosis of Parkinson s disease were randomly assigned to receive pl acebo or 3 to 12 mg of rivastigmine per day for 24 weeks. Primary efficacy varia bles were the scores for the cognitive subscale of the Alzheimer s Disease Ass essment Scale (ADAS cog) and Alzheimer s Disease Cooperative Study Clinici an s Global Impression of Change (ADCS CGIC). Secondary clinical outcomes we re the scores for the Alzheimer s Disease Cooperative Study Activities of Da ily Living, the 10 item Neuropsychiatric Inventory, the Mini Mental State Ex amination, Cognitive Drug Research power of attention tests, the Verbal Fluency test, and the Ten Point Clock Drawing test. RESULTS: A total of 541 patients w ere enrolled, and 410 completed the study. The outcomes were better among patien ts treated with rivastigmine than among those who received placebo; however, the differences between these two groups were moderate and similar to those reporte d in trials of rivastigmine for Alzheimer s disease. Rivastig mine treated patients had a mean improvement of 2.1 points in the score for the 70 point A DAS cog, from a baseline score of 23.8, as compared with a 0.7 point worseni ng in the placebo group, from a baseline score of 24.3 (P < 0.001). Clinically m eaningful improvements in the scores for the ADCS CGIC were observed in 19.8 p ercent of patients in the rivastigmine group and 14.5 percent of those in the pl acebo group, and clinically meaningful worsening was observed in 13.0 percent an d 23.1 percent, respectively (mean score at 24 weeks, 3.8 and 4.3, respectively; P=0.007). Significantly better outcomes were seen with rivastigmine with respec t to all secondary efficacy variables. The most frequent adverse events were nau sea (affecting 29.0 percent of patients in the rivastigmine group and 11.2 perce nt of those in the placebo group, P < 0.001), vomiting (16.6 and 1.7 percent, P < 0.001), and tremor (10.2 and 3.9 percent, P=0.01). CONCLUSIONS: In this placebo con trolled study, rivastigmine was associated with moderate improvements in dementi a associated with Parkinson s disease but also with higher rates of nausea, vo miting, and tremor. BACKGROUND: Cholinergic deficits are prominent in patients who have dementia associated with Parkinson’s disease. We investigated the effects of the dual c holinesterase inhibitor rivastigmine in such patients. METHODS: Patients in whom mildto moderate dementia developed at least 2 years after they received a clinical diagnosis of Parkinson’s disease were randomly assigned to receive pl acebo or 3 to 12 mg of rivastigmine per day for 24 weeks. Primary efficacy varia bles were the scores for the cognitive subscale of the Alzheimer’s Disease Asstification Scale (ADAS-cog) and Alzheimer’s Disease Cooperative Study-Clinici an s Global Impression of Change (ADCS-CGIC). Secondary clinical outcomes we re the scores for the Alzheimer’s Disease Cooperative Study-Activities of Da ily Living, the 10-item Neuropsychiatric Inventory, the Mini-Mental State Exmination, Cognitive Drug Research power of attention tests, the Verbal Fluency test, and the Ten Poi RESULTS: A total of 541 patients w ere enrolled, and 410 completed the study. The outcomes were better among patien ts treated with rivastigmine than among those who received placebo; however, the differences between these two groups were Moderate and similar to those reporte d in trials of rivastigmine for Alzheimer’s disease. Rivastig-mine-treated patients had a mean improvement of 2.1 points in the score for the 70-point A DAS-cog, from a baseline score of 23.8, as compared with a 0.7point worsen in the placebo group, from a baseline score of 24.3 (P <0.001). Clinically m eaningful improvements in the scores for the ADCS CGIC were observed in 19.8 p ercent of patients in the rivastigmine group and 14.5 percent of those in the pl acebo group, and clinically meaningful 7% percent an d 23.1 percent, respectively (mean score at 24 weeks, 3.8 and 4.3, respectively; P = 0.007). Significantly better outcomes wer e seen with rivastigmine with respec t to alThe most frequent adverse events were nau sea (affecting 29.0 percent of patients in the rivastigmine group and 11.2 percents of those in the placebo group, P <0.001), vomiting (16.6 and 1.7 percent, P <0.001) , and tremor (10.2 and 3.9 percent, P = 0.01) CONCLUSIONS: In this placebo-controlled study, rivastigmine was associated with moderate improvements in dementia associated with Parkinson’s disease but also with higher rates of nausea, vo miting, and tremor.