Dextromethorphan/quinidine, whose trade name Nuedexta, is a combination drug containing dextromethorphan and the antiarrhythmic agent quinidine. Quinidine is included to inhibit dextromeththorphan metabolism. For more information go to : https://www.nuedexta.com This pilot-study (NCT01767129) examined the safety and efficacy of dextromethorphan plus quinidine for treating L-dopa induced dyskinesia. People with Parkinson's Disease were randomised to 45mg dextromethorphan and 10mg twice daily, alternated with a placebo.
The main assessment was dyskinesia severity. Dyskinesia severity was a bit lower with dextromethorphan and quinidine than with a placebo, and subsequently significantly lower. Most of the patients rated their dyskinesia "much or very much improved" when taking dextromethorphan and quinidine. Dextromethorphan and quinidine did not worsen Parkinson's Disease motor scores, was generally well tolerated, but was associated with more frequent adverse effects. This study provides preliminary evidence of clinical benefit with dextromethorphan / quinidine for treating L-dopa induced dyskinesia in Parkinson's Disease. Larger studies with a longer treatment duration are needed to corroborate these findings.
Reference : Movement Disorders  Mar 30 [Epub ahead of print] (S.H.Fox, L.V. Metman, J.G.Nutt, M.Brodsky, S.A.Factor, A.E.Lang, L.E.Pope, N.Knowles, J.Siffert) Complete abstract : http://www.ncbi.nlm.nih.gov/pubmed/28370447