Parkinson's Drug Linked to Heart Disease

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http://reuters.com/newsArticle.jhtml?type=healthNews & storyID=2106527Parkinson's Drug Linked to Heart Disease By Alison McCook NEW YORK (Reuters Health) - People with Parkinson's disease who take the drug levodopa to control their symptoms appear to have a higher than average risk of heart disease, US researchers report. It is not clear whether levodopa itself raises heart disease risks, but previous research has shown that the drug can boost body levels of homocysteine, an amino acid associated with an increased risk of stroke and heart disease. These preliminary findings "raise certain concerns" about the safety of levodopa, but are not meant to discourage people from taking the drug, study author Dr. Ramon Diaz-Arrastia told Reuters Health. "I think if patients need levodopa because of (Parkinson's) symptoms, then they should be on it. It's certainly the most effective therapy," he noted. Parkinson's disease is a progressive neurological disorder marked by the loss of brain cells that produce dopamine, a chemical key in controlling muscle activity. When dopamine levels are low, normally coordinated brain regions that control body movement become out of sync, leading to tremors, muscle rigidity, slowed movement and balance and coordination problems. Levodopa is a precursor to dopamine in the brain, and the synthetic version can greatly alleviate patients' symptoms. It does not cure the disorder, though. During the current study, Diaz-Arrastia, of the University of Texas Southwestern Medical Center in Dallas, and his colleagues measured homocysteine levels in blood samples from 235 people with Parkinson's, including 201 who had received levodopa. Diaz-Arrastia and his team also asked participants if they had ever had a heart attack or had undergone open-heart surgery or the artery-clearing procedure angioplasty. People who said they had received levodopa tended to have higher levels of homocysteine in their blood than people who had never taken the drug. People with the highest levels of homocysteine in their blood were more likely to have developed heart disease. The results of the study do not prove that levodopa causes the increases in homocysteine levels and heart disease risk, according to Diaz-Arrastia. That said, he noted that previous studies have suggested that high levels of homocysteine can boost the risk of dementia, and approximately one third of patients with Parkinson's disease eventually develop dementia. So the question arises whether levodopa could either worsen Parkinson's or increase the risk that people with the disease will develop dementia. "That is obviously one of the potential implications of this work," Diaz-Arrastia said. Low levels of vitamin B12 and folic acid, or folate, are most often to blame for increases in homocysteine in the blood, the researcher added. Deficiencies in these B vitamins did not explain the differences in homocysteine levels among Parkinson's patients in the study. Still, Diaz-Arrastia suggested that patients with Parkinson's who discover they have high homocysteine levels take a multivitamin rather than stop therapy with levodopa, if the drug appears to be helping. SOURCE: Archives of Neurology 2003;60:59-64.