Vortioxetine as adjunctive therapy to risperidone for treatment of patients with chronic schizophrenia: A randomised, double-blind, placebo-controlled clinical trial

Introduction and objectives: Vortioxetine, a novel antidepressant, may be an interesting candidate for adjunctive therapy of schizophrenia. Our primary objective was to investigate the effect of vortioxetine on negative symptoms, with the assessment of positive, general psychopathology and total symptoms as our secondary goal. Methods: This was an eight-week randomised, double-blind, placebo-controlled, parallel-group clinical trial, in which 78 inpatients with chronic schizophrenia were stabilised with risperidone (4–6 mg/day) for two months before being assigned to adjunctive vortioxetine (10 mg b.i.d.) or placebo. The patients were assessed using the Positive and Negative Syndrome Scale (PANSS), Extrapyramidal Symptom Rating Scale and Hamilton Depression Rating Scale during the study course. All participants had a PANSS negative symptoms subscale score of ⩾16 at baseline. Sixty-eight patients completed the trial. Results: Vortioxetine improved the negative symptoms score as the primary outcome and total PANSS score as a secondary outcome significantly better than placebo from baseline to end point at week 8, accompanied by significant time × treatment interactions and effect sizes (negative symptoms: mean difference (95% confidence interval (CI)) = −1.82 (−2.73 to −0.92); total scores: mean difference (95% CI) = −2.09 (−3.16 to −1.01). No significant difference was detected for changes in positive symptoms score or PANSS general psychopathology score as the other secondary outcomes from baseline to end point between the two treatment arms. The incidence of adverse events was comparable between groups. Conclusions: This is the first study to provide evidence for the therapeutic effect of vortioxetine on negative symptoms as an adjunctive to treatment with antipsychotics in patients with schizophrenia.