THE EFFECTS OF THE ATYPICAL ANTIPSYCHOTICS CLOZAPINE, REMOXIPRIDE ANDRISPERIDONE ON THE CONTRACTILE CHARACTERISTICS OF RAT SKELETAL-MUSCLEIN-VITRO

The therapeutic use of the atypical antipsychotics clozapine, remoxipr ide and risperidone has been reported to be associated with a reduced occurrence of the extrapyramidal side-effects seen during therapy with classical (or typical) antipsychotics such as trifluoperazine and hal operidol. The aim of this study was to determine the effects of the at ypical antipsychotics clozapine, remoxipride and risperidone on rat sk eletal muscle in vitro. Remoxipride and risperidone did not produce co ntracture in muscle. Clozapine induced a small muscle contracture at h igh concentrations. Pre-treatment of muscle with trifluoperazine or ha loperidol in vitro caused the muscle to display contracture responses to halothane, and haloperidol also potentiated a contracture response to caffeine. Pre-treatment of muscle with remoxipride and risperidone did not induce contracture in response to halothane and did not potent iate caffeine contracture. Clozapine pre-treatment caused muscle fibre bundles to display a small halothane-induced contracture and caused s ignificant potentiation of caffeine-induced contracture. (C) 1997 The Italian Pharmacological Society.