Researchers wanted to try ropinirole on the early stages of PD and in participants who had not begun taking levodopa, often called L-dopa. L-dopa, which helps the remaining cells make dopamine in the brain to restore dopamine deficiency, has been the gold standard for treating Parkinson's disease for some 30 years.
Participants underwent a PET scan at the beginning the trial to determine the loss of dopamine in the brain, particularly in the substantia nigra and putamen. When the radioactive tracer 18fluorodopa or 18F-dopa (a positron emitter) is injected, the 3D PET scanner highlights these losses or changes in the brain. The 18F-dopa uptake marks the quantity of functioning dopamine-producing brain cells remaining.
Participants were then randomized to take ropinirole, a dopamine agonist, (93 participants) or L-dopa (93 participants) three times a day for two years. At the end of the trial, another PET scan was taken and compared to the previous scan two years earlier. Investigators found clear evidence, with the use of a PET scan, that progression of the loss of dopamine function was significantly slowed by over 30 percent in participants taking ropinirole.
"These findings could certainly mean a better quality of life for a longer period of time in PD patients," Dr. Watts explains. "Progression of the loss of dopamine function over 10 years can now possibly be stretched to 13 years by starting and maintaining treatment with ropinirole. These findings will help guide the treatment of early PD and could be an important factor in changing the treatment methods of PD."
Investigators also determined the incidence of dyskinesia, involuntary movements (fragmented or jerky motions) that can result from dopaminergic therapy, was greatly reduced in participants taking ropinirole.