The effect of mirtazapine add on therapy to risperidone in the treatment of schizophrenia: a double-blind randomized placebo-controlled trial.

It has been reported that mirtazapine would be helpful for treating negative symptoms in schizophrenia. Nevertheless, the results are contradictory so far. This study was designed to investigate the effect of mirtazapine added to risperidone as augmentation therapy in patients with chronic schizophrenia and prominent negative symptoms in a double-blind and randomized clinical trial. Eligible participants in the study were 40 patients with chronic schizophrenia with ages ranging from 19 to 49 years. All patients were inpatients and were in the active phase of the illness, and met DSM-IV-TR criteria for schizophrenia. Patients were allocated in a random fashion 20 to risperidone 6 mg/day plus mirtazapine 30 mg/day and 20 to risperidone 6 mg/day plus placebo. The principal measure of the outcome was Positive and Negative Syndrome Scale (PANSS). The mirtazapine group had significantly greater improvement in the negative symptoms and PANSS total scores over the eight-week trial. Therapy with 30 mg/day of mirtazapine was well tolerated and no clinically important side effects were observed. The present study indicates mirtazapine as a potential combination treatment strategy for chronic schizophrenia particularly for negative symptoms.