A Randomized, Double-Blind Comparison of Risperidone Versus Low-Dose Risperidone Plus Low-Dose Haloperidol in Treating Schizophrenia

Monotherapy is recommended for schizophrenia treatment, but the risk-benefit issue of antipsychotic drug combination (except for clozapine) remains unclear. Risperidone, an atypical antipsychotic drug, has a lower incidence of extrapyramidal syndrome but higher risks of prolactinemia and metabolic syndrome than haloperidol, a typical agent. This study compared efficacy and safety of risperidone monotherapy versus low-dose risperidone plus low-dose haloperidol in schizophrenia. In this 6-week, double-blind study, patients were randomized to the combination group (2-mg/d risperidone plus 2-mg/d haloperidol, n = 46) or the monotherapy group (4-mg/d risperidone, n = 42). Efficacy assessments included Clinical Global Impression-Severity, Positive and Negative Syndrome Scale and subscales, Calgary Depression Scale, Global Assessment of Functioning, and Medical Outcomes Study Short-Form 36. Safety was rigorously monitored. Response was defined as 30% reduction in the Positive and Negative Syndrome Scale total score. The 2 treatment groups were similar in (1) demographic and clinical characteristics at baseline, (2) response rate, and (3) improvement in various psychopathological measures and quality of life at end point. The monotherapy group had a higher increase in prolactin levels (P = 0.04) and Simpson-Angus Scale scores (P = 0.04) and a higher percentage of biperiden use (P = 0.045). There were no significant between-group difference in changes in weight, vital signs, corrected QT interval, liver/renal function, fasting glucose level, and lipid profiles. The findings suggest that risperidone monotherapy may yield higher prolactin levels than a combination of low-dose risperidone plus low-dose haloperidol. The 2 treatment groups are similar in efficacy, life quality, and other safety profiles. Future long-term studies are warranted.