Complications of therapy in Parkinson's disease.

Despite several more effective combinations, the incidence of disability and intractable complications from levodopa therapy for Parkinson's disease is unchanged. Many of these appear to be related to the development of denervation hypersensitivity as well as to drug tolerance and loss of effect. They include dyskinesia, `wearing off' phenomenon, `on-off' phenomenon, and various psychic changes. More current forms of therapy with bromocriptine and drug holidays are described, emphasizing methods of preventing and controlling the incapacitating complications associated with long term drug therapy. Some future therapeutic considerations are also described.