More evidence on additive antipsychotic effect of adjunctive mirtazapine in schizophrenia: an extension phase of a randomized controlled trial.

OBJECTIVE

Adjunctive mirtazapine improved negative symptoms of schizophrenia in several studies. Recently, we found an improvement also in positive symptoms when mirtazapine was added to first generation antipsychotics (FGAs) in a 6 week randomized controlled trial (RCT). The short duration of that trial was its limitation. This study aimed to explore whether longer treatment is worthwhile.

METHOD

Completers of the RCT (n = 39) received open-label add-on mirtazapine for additional 6 weeks. The Positive and Negative Syndrome Scale (PANSS) total score (primary outcome) and several other clinical parameters were measured prospectively.

RESULTS

During the open-label phase, significant improvement was achieved in all parameters, with an effect size of 0.94 (CI 95% = 0.45-1.43) on the primary outcome and an impressive additive antipsychotic effect. Patients who received mirtazapine during both phases demonstrated greater improvement in positive symptoms (29.6% versus 21.2%, p = 0.027) than those who received mirtazapine during open-label extension phase only.

CONCLUSIONS

These findings support our previous data on the additive antipsychotic effect of mirtazapine in FGAs-treated schizophrenia. Mirtazapine may be effective in other symptom domains, too. Longer duration of mirtazapine treatment may yield additional benefits. If these results will be confirmed in larger studies, add-on mirtazapine may become a feasible option in difficult-to-treat schizophrenia.