Efficacy of pimozide augmentation for clozapine partial responders with schizophrenia.

Introduction: A substantial number of patients with treatment-resistant schizophrenia respond only partially to clozapine. Therefore, it has been common practice to use augmentation strategies to maximize clozapine's effect. But the efficacy of this strategy remains poorly established. We have conducted a randomized double-blind placebo controlled clinical trial in patients with schizophrenia currently receiving clozapine with partial response, and tested the efficacy of pimozide augmentation on positive and negative symptoms and also on neurocognitive measures.

Methods: Thirty-two outpatients enrolled in the clinical trial and 28 completed. Patients with adequate blood levels of clozapine were randomized to pimozide vs placebo and participated in the trial for 12 weeks receiving monthly assessments for Brief Psychiatric Rating Scale (BPRS) and Schedule for Assessment of Negative Symptoms (SANS), and weekly assessments for electrocardiogram (EKG), and side effects. Neurocognitive tests measuring verbal fluency, working memory, motor and attention/executive function were obtained at study entry and end of the trial.

Results: We found no significant effect of pimozide on BPRS total, psychosis and depression subscale items, SANS scores or QTc interval. Neurocognitive measures did not show significant improvement either.

Discussion: In this well controlled clinical trial of patients with treatment-resistant schizophrenia currently receiving clozapine, pimozide augmentation was not an effective strategy to maximize the benefit for better control of positive and negative symptoms or improving neurocognitive function.