NEW YORK (Reuters Health) - The prolonged use of antimuscarinic drugs in subjects with Parkinson's disease appears to accelerate beta-amyloidosis and neurofibrillary tangle formation, according to autopsy findings.

Dr. Elaine K. Perry, of Newcastle General Hospital in Newcastle upon Tyne, UK, and colleagues reviewed case records and neuropathology reports of patients age 70 or above with Parkinson's disease but no dementia. Plaques and tangles were rated on a 0 to 5 scale, where 0 represented absence, and 5 represented numerous.

Eighteen patients treated with antimuscarinic agents for more than 2 years had significantly higher plaque density (2.50) compared with short-term treatment (0.60, p = 0.00005) and with untreated patients (1.11, p = 9.005). Findings were similar for tangles, with ratings of 0.94, 0.50, and 0.43, respectively.

The authors note that the tremorlytics prescribed for these patients -- benztropine, orphenadrine or trihexyphenidyl -- have been largely replaced by more effective agents. However, oxybutynin is still often used to treat bladder dysfunction in patients with Parkinson's disease.

"If our findings are substantiated," they conclude, "they would suggest that chronic antimuscarinic medication may not be appropriate in older patients."

Dr. Allan I. Levey of Emory University School of Medicine in Atlanta, Georgia, echoes this suggestion in an accompanying editorial. He notes that polypharmacy with anticholinergic drugs is common in the elderly. While many such drugs are clearly beneficial, "the deleterious consequences of anticholinergics could be more serious than currently recognized if these drugs influence brain pathology."

He writes, "The hypothesis that cholinomimetics may reduce tangle formation needs to be tested clinically, because this might represent an important first step forward for neuroprotective strategies for tauopathies." Meanwhile, "physicians should prescribe anticholinergics judiciously, particularly in the elderly.

Ann Neurol 2003;54:144-146,235-238.

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