Double-blind comparison of olanzapine versus clozapine in schizophrenic patients clinically eligible for treatment with clozapine

Background: The treatment of schizophrenic patients who fail to respond to adequate trials of neuroleptic drugs is a major challenge. Clozapine has been one treatment option; however, it is not universally effective and is limited in its use by safety concerns. With the introduction of newer agents, their-performance relative to clozapine is of great clinical interest, Methods: The primary objective of this study was to evaluate the efficacy and safety of olanzapine versus clozapine among treatment resistant DSM-IV schizophrenic patients. The study,vas primarily designed to demonstrate the noninferiority of olanzapine compared to clozapine after 18 weeks of double-blind treatment. Conclusions were based on the one-sided lower 95% confidence limit about the treatment effect observed from the primary efficacy variable (Positive and Negative Syndrome Scale (PANSS] Total). Results: Mean changes from baseline to end point in PANSS Total score, using a last observation carried forward technique, showed that both agents were comparably effective in neuroleptic resistant patients, i.e,, demonstrated the noninferiority of olanzapine when compared to clozapine. Overall, significantly fewer olanzapine-treated patients (4%) discontinued for an adverse event than their clozapine-treated (14%) counterparts (p =.022). Among spontaneously reported adverse events, increased salivation, constipation, dizziness, and nausea were reported significantly more often among clozapine-treated patients, whereas only dry mouth was reported more often among olanzapine-treated patients. Conclusions: Olanzapine was demonstrated to be noninferior to clozapine and better tolerated among resistant schizophrenic patients clinically eligible for treatment with clozapine. Biol Psychiatry 2001;49:52-63 (C) 2001 Society of Biological Psychiatry.