Parkinson's Drug Linked to Heart Risk
Patients Taking Levodopa Have Elevated Homocysteine Levels
Jan. 28, 2003 -- The Parkinson's disease drug levodopa may increase the risk of heart disease by raising blood levels of the homocysteine. In a new study, patients who took the drug had higher than normal homocysteine levels, while other Parkinson's patients did not.
Although the findings are preliminary and need to be confirmed, they are not the first to suggest that the widely prescribed Parkinson's drug raises homocysteine levels. And elevated levels of the amino acid have been linked to an increased risk of heart attack and stroke. The most common cause of high homocysteine is a deficiency of folic acid or vitamin B12. But patients taking levodopa for Parkinson's may have elevated levels as a result of the medication itself.
Researcher Ramon Diaz-Arrastia, MD, PhD, tells WebMD that Parkinson's patients taking levodopa should not be overly concerned by the early findings.
"We certainly aren't telling people to stop taking their levodopa, but this is something that patients may want to bring up with their physicians," he says. "It is pretty easy and cheap to get your homocysteine level tested, and patients may be able to lower their homocysteine with vitamin therapy."
Diaz-Arrastia says recent studies from Japan and Germany found higher than normal homocysteine levels among patients on levodopa, but it was not clear whether the drug or the disease itself was responsible for the increase.
In their study, reported in the January issue of the journal Archives of Neurology, Diaz-Arrastia and colleagues from University of Texas Southwestern Medical Center in Dallas measured blood homocysteine levels in 201 Parkinson's patients on levodopa and 35 patients who had never taken the drug. The levodopa patients had 31% higher homocysteine levels than patients who had never taken the drug.
The researchers also found that patients with elevated homocysteine levels were far more likely to have coronary artery disease. Patients on levodopa tended to be older than patients not taking the drug and most had had Parkinson's longer -- both risk factors for increased homocysteine levels. But Diaz-Arrastia says the researchers attempted to control for this in their study.
It is estimated that one-third of people with Parkinson's disease develop dementia, and Diaz-Arrastia says his findings may have implications for these patients. Several large studies are currently examining whether elevated homocysteine is a risk factor for Alzheimer's and other dementia-related conditions. The jury is still out, but if the link is established the researcher says it could explain the high incidence of dementia among Parkinson's patients.
"It has been thought that dementia was associated with the disease itself, but this certainly raises the possibility that the therapy may be putting these folks at risk," he says.
He adds that patients taking levodopa may be able to lower their homocysteine levels by taking supplements -- specifically folic acid, and vitamins B12 and B6.
Donald Jacobsen, PhD, who directs the Laboratory for Homocysteine Research at the Cleveland Clinic Foundation, tells WebMD that taking supplements of these vitamins can dramatically lower homocysteine levels, even in those who get the recommended levels of the vitamins in their diets.
"There are many studies showing that homocysteine accelerates the progression of vascular disease," he tells WebMD. "I think there will soon be significant evidence that you can slow this down by lowering homocysteine levels with these supplemental vitamins. The link with Alzheimer's is less conclusive, but we will probably have some answers in a few years."