Management of patients who fail to respond to levodopa therapy.

Nonresponders to levodopa therapy include patients with parkinsonism who fail to respond to a well-tolerated therapeutic dosage, those who lose an initially positive response, and those who develop severe and dose-limiting side effects. Initial failures may be due to inadequate dosage, drug interactions or inaccurate diagnosis. Loss of response suggests the need for a thorough medical evaluation. Severe side effects such as nausea and vomiting may be managed with adjuvant agents; dystonia and a variety of paradoxical responses may preclude the use of levodopa, and amantadine or anticholinergic agents should be considered as alternatives.