Paradoxical reaction to L-dopa in schizophrenic patients

The authors administered 6 g of L-dopa to 8 schizophrenic patients and 750 mg of chlorpromazine to 7 schizophrenic patients. Chlorpromazine showed only a modest advantage over L-dopa and only on some Brief Psychiatric Rating Scale factor scores, and at maximum dosage the thought disturbance factor score in the L-dopa-treated group was not worse than at baseline. The results suggest that L-dopa is associated more with toxic than with schizophreniform symptoms and that there is adaptation to its effects. The authors discuss implications of these findings for the dopamine hypothesis of schizophrenia.