Long-term Parkinson’s treatment sheds bad rep

Taking levodopa early in the disease doesn’t increase side effects

Many doctors delay prescribing an effective treatment for Parkinson’s disease out of fear that the drug will cause side effects if given too early. That fear may be unfounded, a new study suggests.

Since the 1960s, doctors have prescribed levodopa to ease the slow movements, tremors and rigid muscles that come with Parkinson’s. But this relief appears to come at a price. Earlier studies indicated that prolonged levodopa use at high doses caused a different set of problems, such as uncontrollable movements. 

By comparing people with Parkinson’s in Ghana, where levodopa is hard to come by, with patients from Italy, where the drug is routinely used, scientists have now found that side effects are no worse in people who start levodopa early. The results appear July 17 in Brain.

“We believe our findings may wipe away the phobia of levodopa,” says study coauthor Roberto Cilia of the Parkinson Institute in Milan.

Because doctors didn’t have a good way to compare people who hadn’t taken levodopa with those who had, it’s been difficult to separate the effects of the disease from the effects of the medicine, says neurologist Mark Stacy of Duke University. “We lived with that until this manuscript,” he says. “This paper was a very clever way to look at that.”

As part of a humanitarian effort, Cilia and colleagues began treating people with Parkinson’s in Ghana, where medicines such as levodopa are often scarce. The researchers realized that the Ghanaian patients offered a way to study how Parkinson’s progresses in the absence of the drug.

The researchers treated and monitored people with Parkinson’s for about four years. On average, 91 Ghanaians in the study first received levodopa 4.2 years after developing the disease; 182 Italians received the drug about two years sooner. Despite those additional years on levodopa, Italian patients had no more motor problems brought on by levodopa than did the Ghanaians, Cilia and colleagues report.

That similarity suggests that the length of levodopa use doesn’t influence the severity of its movement side effects. In fact, some Ghanaian patients showed side effects just hours or days after their very first dose, the researchers found. As in previous studies, higher doses of levodopa were associated with more severe side effects.

Along with dose, stage of Parkinson’s disease is what determines the severity of the levodopa response, not the length of time someone has taken the drug, says study coauthor Gianni Pezzoli, also of the Parkinson Institute.

Stacy says the results will allow him to “make a stronger case to begin patients on levodopa when I think it’s an appropriate time.” Early levodopa treatment can improve people’s lives for years, he says.

Pezzoli, Cilia and colleagues are working on a way to grow a plant, Mucuna pruriens, that’s naturally packed with levodopa. They hope people in developing countries will grow the seeds, bringing the medicine to more people who need it.

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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