Augmenting clozapine with sertindole: a double-blind, randomized, placebo-controlled study.

Clozapine augmentation with antipsychotic drugs is widely used despite sparse evidence supporting this strategy. Sertindole is a nonsedating atypical antipsychotic drug with low affinity for cholinergic receptors, which makes it potentially suitable for augmentation of clozapine. The study design was a 12-week, double-blind, randomized, placebo-controlled study including patients with International Statistical Classification of Diseases, 10th Revision schizophrenia (F20.0-F20.3) and treated with clozapine for at least 6 months who had not achieved sufficient response. Patients were randomized 1:1 to either sertindole 16 mg or placebo, and assessment was done at baseline and after 6 and 12 weeks. Assessment included the Positive and Negative Syndrome Scale, Clinical Global Impression, Udvalg for Kliniske Undersøgelser, World Health Organization Quality of Life Brief, Drug Attitude Inventory, fasting glucose, lipids, and electrocardiogram. Clozapine augmentation with sertindole was not superior to placebo regarding total score or subscale score of the Positive and Negative Syndrome Scale, Clinical Global Impression, World Health Organization Quality of Life Brief, or Drug Attitude Inventory. No increased adverse effects compared with placebo were found. Four patients randomized to sertindole experienced a significant worsening of psychosis, and 2 of them required psychiatric admission. Metabolic parameters were unchanged during the study, but augmentation of clozapine with sertindole was associated with a 12-millisecond (SD, 20-millisecond) QTc prolongation compared with 0 millisecond (SD, 20 milliseconds) in the placebo group (P < 0.03). Augmentation with sertindole showed no benefits compared with placebo. Psychiatrists should be aware that augmentation might not add any benefits for the patients and in some cases worsen psychosis.