A parallel group double-blind comparative trial was conducted to study the efficacy and safety of risperidone compared with haloperidol. After a one-week wash-out, 35 chronic schizophrenic patients (17 males, 18 females) were randomly assigned to one of two groups for eight weeks of double-blind treatment. The patients' psychopathology was assessed by means of the Positive and Negative Syndrome Scale for Schizophrenia (PANSS) and the Clinical Global lmpression (CGl). Safety assessments included the Extrapyramidal Symptom Rating Scale (ESRS). the UKU Side Effect Rating Scale, vital signs, body weight, ECG and laboratory screening. Thirty-two patients completed the trial : there were 3 dropouts in the risperidone group. The results on the PANSS and CGl indicate that the mean changes from baseline on the total PANSS score and on the total BPRS score were comparable in both treatmetn groups. The number of patients where a clinical improvement at least 20% reduction in baseline score was also similar in both treatmetn groups. Risperidone caused less extrapyramidal symptoms and less side effects in UKU scale than haloperidol. No significant ECG changes were induce. no relevant changes in blood pressure or clinical laboratory parameters were
observed. This study has demonstrated that the combined serotonin 5-HT2 and dopamine-D2 antagonist risperidone is an antipsychotic as potent as haloperidol. Risperiodne causes less extrapyramida. Symptoms, and is petter tolerated than haloperidol.