Jan. 4, 2007 -- The epilepsy drug zonisamide may help curb the tremors and other movement problems of Parkinson's, a Japanese study shows.
Zonisamide is sold in the U.S. generically and under the brand name Zonegran.
In Parkinson's disease, the brain cells that make dopamine, a chemical that helps control the body's movements, gradually falter and die. Symptoms include tremor, movement problems, and unsteady balance.
The new study on zonisamide for Parkinson's comes from researcher Miho Murata, MD, PhD, of Japan's National Center of Neurology and Psychiatry, and colleagues. It appears in the Jan. 2 issue of Neurology.
Murata's team studied 279 Japanese Parkinson's patients then taking levodopa and other Parkinson's drugs.
The patients had shown "insufficient response" to those drugs, the researchers write.
They note that the patients had been taking levodopa doses lower than those typically used in the U.S., but said they probably weren't undertreated.
The researchers randomly assigned patients to take either zonisamide in one of three doses (25, 50, or 100 milligrams) or a placebo every day for 12 weeks.
All the patients were required to keep taking their levodopa and were allowed to continue any other Parkinson's drugs they were using before the study began.
The researchers tracked changes in the patients' movement problems during the 12-week study.
Patients taking the zonisamide showed more improvement in their Parkinson's movement symptoms than those on the placebo.
Those benefits included a drop in Parkinson's-related tremors and involuntary movements.
However, zonisamide didn't cure Parkinson's or completely relieve movement symptoms.
Zonisamide trumped the placebo regardless of dosage.
The percentage of patients with at least a 30% drop in Parkinson's movement symptoms were:
- Placebo: 22%
- 25 mg/day zonisamide: 35%
- 50 mg/day zonisamide: 39%
- 100 mg/day zonisamide: 32%
Patients taking 50 or 100 mg/day of zonisamide had the least amount of daily "off time" -- time when their medication had worn off.
Zonisamide was "safe, effective, and well tolerated," the researchers write.
The drug's side effects -- which included sleepiness, apathy, weight loss, and constipation -- were more common with the 100 mg daily dose.
The researchers aren't recommending zonisamide for Parkinson's disease yet. They say longer, more diverse studies are needed.
It's not clear how zonisamide eased Parkinson's symptoms. Murata's team says the drug may boost dopamine production, but they didn't test that theory.
The study was funded by Dainippon Sumitomo Pharma, which developed zonisamide. Zonegran is now licensed exclusively by the drug company Eisai.