Patients beginning to experience the muscle rigidity and other symptoms of Parkinson’s disease typically receive levodopa. This drug spurs nerve cells to replenish depleted supplies of dopamine, an essential neurotransmitter that facilitates muscle movement.
However, some physicians instead prescribe dopamine agonists, drugs that mimic dopamine. These drugs bind to receptors on nerve cells, making them react as they would to dopamine.
For years, scientists have debated which approach is better. Both drugs cause side effects, particularly dyskinesia, which is involuntary movement including twitching, nodding, and jerking.
Researchers now report that patients randomly assigned to routinely take the dopamine agonist ropinirole report fewer side effects than patients getting regular doses of levodopa do.
The scientists treated 177 patients with ropinirole and 88 with levodopa. After 5 years, 20 percent of the first group showed dyskinesia resulting from the treatment, while 45 percent of the second group had such problems, the researchers report in the May 18 New England Journal of Medicine. About two-thirds of the ropinirole group received levodopa occasionally to alleviate severe Parkinson’s symptoms.
“Our findings show convincingly that when you start treating a patient with ropinirole, and you use levodopa only as a second-step supplement, you have the same control of parkinsonian symptoms as with levodopa therapy but with less levodopa-induced abnormal movement,” says study coauthor Olivier Rascol, a neurologist at Toulouse University Hospital in France.
Because it works well in many people, levodopa is the current standard against which Parkinson’s medications must be measured. However, its effect dissipates with constant use.
Thus, replacing levodopa with ropinirole can “preserve levodopa efficacy,” Rascol says.