Behavioral effects of sertindole, risperidone, clozapine and haloperidol in Cebus monkeys.

Extrapyramidal side effects (EPS) are major limitations to neuroleptic treatment of psychoses. To evaluate further the behavioral characteristics of the novel antipsychotic agents, a wide range of single intramuscular doses of sertindole (0.1-2.5 mg/kg IM), risperidone (0.01-0.25 mg/kg IM), clozapine (1.0-25.0 mg/kg IM), and haloperidol (0.01-0.25 mg/kg IM) were blindly evaluated at weekly intervals in Cebus monkeys previously sensitized to neuroleptics. All drugs except clozapine produced dystonia and parkinsonian symptoms, but haloperidol and risperidone were 50-100 times more potent than sertindole in producing EPS. Sertindole, risperidone and haloperidol had no significant sedative effects, whereas clozapine produced dose related sedation. Risperidone, clozapine and haloperidol but not sertindole decreased locomotor activity. Sertindole, risperidone and clozapine had a calming effect at doses below the EPS threshold, unlike haloperidol. Sertindole has many behavioral effects in nonhuman primates that are similar to those seen with the new antipsychotics, risperidone and clozapine, which suggests a favorable antipsychotic benefit/risk ratio in the clinic, especially regarding EPS.