Abstract: The invention provides a method, and dosage form therefor, of treating impaired motor function associated with Parkinson's disease, anti-Parkinson's drug treatment, e.g. L-Dopa therapy, and/or dementia associated with Parkinson's disease. The invention includes the combined administration of an NMDA receptor antagonist and an antidepressant, e.g., the combination of amantadine and citalopram or venlafaxine, or an NMDA receptor antagonist and an anxiolytic agent, e.g., amantadine and buspirone or trazodone, for the amelioration of undesired tremors, akinesia, dyskinesia, or bradykinesia associated with one or more different disorders or diseases. The drugs can be included in a single dosage form. One embodiment includes a combination dosage form containing each drug in controlled release forms. Another embodiment includes a combination dosage form providing a controlled release of an NMDA receptor antagonist and a rapid release of a neuroactive agent after administration to a subject.