OLANZAPINE - A REVIEW OF ITS PHARMACOLOGICAL PROPERTIES AND THERAPEUTIC EFFICACY IN THE MANAGEMENT OF SCHIZOPHRENIA AND RELATED PSYCHOSES

Olanzapine is a thienobenzodiazepine derivative which displays efficac y in patients with schizophrenia and related psychoses. It has structu ral and pharmacological properties resembling those of the atypical an tipsychotic clozapine and an improved tolerability profile compared wi th the classical antipsychotic haloperidol. In several large, well con trolled trials in patients with schizophrenia or related psychoses, ol anzapine generally 5 to 20 mg/day was at least as effective as haloper idol (5 to 20mg) and more so than placebo, as assessed by overall rati ng scales for psychoses. Olanzapine improved negative symptoms to a gr eater extent than haloperidol in 2 of 3 comparative trials, including the largest trial. Efficacy of olanzapine has a rapid onset (within 1 to 2 weeks). Its clinical benefits appear to be maintained for treatme nt periods of up to 1 year, as shown by analysis of the extension phas e of several trials demonstrating decreased probability of hospitalisa tion over this period, compared with haloperidol. Preliminary data sug gest the drug may also improve quality of life. Olanzapine was associa ted with significantly fewer adverse movement disorders (e.g. akathisi a, dystonia, hypertonia, extrapyramidal symptoms) than haloperidol. Th ere have been no reports of agranulocytosis (as occurs with clozapine) or any other haemotoxicity attributed to olanzapine, and the drug has shown minimal effect on prolactin levels. Transient increases in leve ls of hepatic transaminases seem to be clinically unimportant. The onl y events recorded more frequently during olanzapine than during halope ridol therapy were weight gain, dry mouth and increased appetite. Alth ough the antipsychotic activity of olanzapine has been well demonstrat ed, its efficacy in refractory schizophrenia and its place relative to other atypical antipsychotics remain to be determined. Nevertheless, if the long term tolerability profile of olanzapine is confirmed, the drug should provide a valuable therapeutic alternative in the manageme nt of schizophrenia and related psychoses.