RISPERIDONE IS ASSOCIATED WITH BLUNTING OF D-FENFLURAMINE EVOKED SEROTONERGIC RESPONSES IN SCHIZOPHRENIA

The high 5-HT affinity of some atypical antipsychotic agents is though t to contribute to their clinical efficacy. We examined central 5-HT r esponses in two groups of ten schizophrenic patients by measuring seru m prolactin and cortisol responses to the neuroendocrine challenge D-f enfluramine. One group of patients with schizophrenia was tested after a 2-week neuroleptic free period. A similar group were tested after a mean of 12 weeks treatment with the atypical antipsychotic risperidon e. A significant elevation of baseline serum prolactin levels, consist ent with dopaminergic antagonism was seen after risperidone treatment. Significantly reduced 5-HT mediated serum prolactin responses were se en in risperidone treated patients. D-fenfluramine evoked serum prolac tin responses were positively correlated with positive but not negativ e schizophrenic symptoms for all 20 patients. Risperidone treatment wa s associated with a significant functional in-vivo 5-HT antagonism sim ilar to clozapine. 5-HT antagonism may contribute to the efficacy of r isperidone against positive schizophrenic symptoms. Int Clin Psychopha rmacol 13:199-203 (C) 1998 Lippincott Williams & Wilkins.