A drug sometimes used to treat Alzheimer’s disease can also moderately improve dementia caused by Parkinson’s disease, according a report in this week’s New England Journal of Medicine.

Rivastigmine, marketed under the name Exelon, leads to clinically significant improvement in about 20 percent of Parkinson’s patients - about the same as that achieved in patients with Alzheimer’s disease - Dr. Murat Emre, at Istanbul University in Turkey, and colleagues report.

The team’s study involved 329 Parkinson’s disease patients who were assigned to various doses of rivastigmine and 161 who were given an inactive placebo.

After 24 weeks, subjects in the rivastigmine group exhibited an average improvement of 2.1 points on a standard dementia scale, “compared with a worsening of 0.7 points in the placebo group,” the investigators report.

“Clinically meaningful (moderate or marked) improvement” occurred in 19.8 percent of those in the rivastigmine group and in 14.5 percent of those in the placebo group,” the authors note.

The most common adverse effects associated with rivastigmine were nausea, vomiting and tremor.

Given the relatively modest benefit and possibility of uncomfortable side effects, “physicians should evaluate each patient individually before deciding to initiate treatment with rivastigmine,” the authors advise.

In a related editorial, Dr. Daniel Z. Press writes, “The results are not as impressive as one would have hoped.”

Press, of Harvard Medical School in Boston, recommends that if patients who are given a drug like rivastigmine do not exhibit a clear response after 8 to 12 weeks, the medication should be tapered and discontinued.

SOURCE: New England Journal of Medicine, December 9, 2004.