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.
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).
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.
Olanzapine was demonstrated to be noninferior to clozapine and better tolerated among resistant schizophrenic patients clinically eligible for treatment with clozapine.