A study has found a cough suppressant and a drug tested as a schizophrenia therapy help curb disabling side effects of levodopa, a Parkinson's disease medication.
The mouse model based study, led by Melanie A. Paquette, Ph.D., postdoctoral fellow in the Department of Behavioural Neuroscience, OHSU School of Medicine, and the PVAMC, found that Dextromethorphan, used in such cold and flu medications as Robitussin, Sucrets, Triaminic and Vicks, suppressed dyskinesias in rats.
The researchers also found that BMY-14802, a drug previously tested in people with schizophrenia and found to be safe, although not effective in treating schizophrenia symptoms, suppressed dyskinesias in rats more effectively than dextromethorphan did, suggesting that BMY-14802 might work to block dyskinesias in people with Parkinson's.
Dyskinesias are the spastic or repetitive motions that result from taking levodopa, or L-dopa, over long periods. "These results were unexpected, but very exciting. We have filed a patent for the use of BMY-14802 for dyskinesias and we hope to get funding to begin human trials very soon," Paquette said.
The findings also stated the value of the rat model for dyskinesias that was used in the study. Previous studies have shown that the drug amantadine was effective in treating dyskinesias in both humans and rats. "Basically, these two drugs work to block dyskinesias in both humans and rats, and that means the rats are a good model to screen potential drug treatments for humans with dyskinesias," Paquette said.
But BMY-14802, which is an antagonist at sigma-1 receptor sites in the brain, "worked much better than dextromethorphan," an antagonist at N-methyl-D-aspartate (NMDA) receptors. "There's something special about BMY-14802. The effect on dyskinesias is really striking and I've repeated it several times, so it's a reliable finding. It's a very exciting result," Paquette said.