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Monday 01 January 2001

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

By: Tollefson GD, Birkett MA, Kiesler GM, Wood AJ; Lilly Resistant Schizophrenia Study Group.

Biol Psychiatry 2001 Jan 1;49(1):52-63

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 was 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.

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