Low-dose clozapine for the treatment of Parkinson's disease in a patient with schizophrenia.

Clozapine is known to be beneficial for the treatment of dopamine agonist-induced psychotic states in patients with Parkinson's disease (PD). Many reports have suggested that it may also be efficacious for the treatment of parkinsonian tremor. We describe a patient with schizophrenia in whom early-onset PD appeared after treatment with antipsychotic drugs. When the parkinsonian symptoms proved resistant to anticholinergic agents, we introduced a trial with up to 50 mg clozapine daily, which yielded a prompt and dramatic response. Thereafter, the parkinsonian symptoms reappeared each time the patient discontinued clozapine and rapidly disappeared on its repeat initiation. There was also a marked improvement in his psychotic and depressive symptoms. This report suggests that some patients with concomitant schizophrenia and PD-a difficult treatment challenge-may benefit from clozapine treatment alone for both disorders.