This invention provides methods of treating motor disorder side effects associated with the administration of levodopa to a subject having Parkinson's disease, by administering eltoprazine or a pharmaceutically acceptable acid addition salt thereof in doses and dosing schedules which result in beneficial antidyskinetic effects for the subject. In particular, the invention provides methods for reducing dyskinesia associated with Parkinson's disease treatments, and effective doses and dosing regimens of eltoprazine or a pharmaceutically acceptable acid addition salt thereof.
