Parkinson's drug may hasten Alzheimer's

Common treatment might exacerbate brain build-ups.
28 July 2003

HELEN PEARSON

5-10% of Parkinson's patients receive antimuscarinic drugs. © GettyImages

Drugs given to Parkinson's patients and the elderly may hasten the onset of Alzheimer's disease, a preliminary study hints.

Antimuscarinic drugs are prescribed to an estimated 5-10% of Parkinson's patients to help control tremors, bladder problems and depression. They block some of the actions of a brain chemical called acetylcholine.

Parkinson's patients who had taken the medicines for more than two years had roughly twice the usual level of protein usual level of protein clumps and tangles compared to those not on drugs, found Elaine Perry of Newcastle General Hospital, UK. Clumps and tangles are characteristic of Alzheimer's patients. Perry's team examined 120 records from a British brain bank, obtained from patients over 70 years of age¹.

Doctors should not jump to switch therapies, the team says. None of the patients examined had actually shown symptoms of Alzheimer's. And antimuscarinic drugs are used less and less to treat Parkinson's now, because of short-term side-effects such as confusion.

But there is cause for concern, believes Allan Levey, who studies nervous-system disease at Emory School of Medicine in Atlanta, Georgia. Millions of people take drugs such as tricyclic antidepressants, antihypertensives and antihistamines that block acetylcholine indirectly, he points out, even though these medicines target other molecules.

"It's hard to find elderly people who aren't on them," Levey says. New studies should monitor whether these patients are at greater risk of Alzheimer's, he suggests.

Up side

More optimistically, if drugs that block acetylcholine encourage Alzheimer's, then others that fire up the acetylcholine system might stop or slow the brain disease. 'That's the more exciting aspect," Perry says.

Already acetylcholine boosters, such as rivastigamine, are frequently used to ease the symptoms of Alzheimer's. But they were not thought to deal with the plaques of twisted beta-amyloid protein that characterize the disease and are implicated in dementia.

Animal studies suggest that acetylcholine stimulants stall plaque growth; human trials are under way to explore whether the drugs protect people from Alzheimer's.

1. Perry, E. K. et al. Increased Alzheimer pathology in Parkinson's disease related to antimuscarinic drugs. Annals of Neurology, 54, 235 - 238, (2003). |Homepage|