Olanzapine and risperidone, both second-generation antipsychotic agents, represent two different pharmacologic strategies. Although they share some in vitro properties, they differ by virtue of their chemical structure, spectrum of receptor binding affinities, animal neuropharmacology, pharmacokinetics, and in vivo neuroimaging profile. Based on such differences, it was hypothesized that the two compounds would show distinct safety and/or efficacy characteristics. To test this hypothesis, an international, multicenter, double-blind, parallel-group, 28-week prospective study was conducted with 339 patients who met DSM-IV criteria for schizophrenia, schizophreniform disorder, or schizoaffective disorder. Results of the study indicated that both olanzapine and risperidone were safe and effective in the management of psychotic symptoms. However, olanzapine demonstrated significantly greater efficacy in negative symptoms (Scale for Assessment of Negative Symptoms summary score), as well as overall response rate (> or = 40% decrease in the Positive and Negative Syndrome Scale total score). Furthermore, a statistically significantly greater proportion of the olanzapine-treated than risperidone-treated patients maintained their response at 28 weeks based on Kaplan-Meier survival curves. The incidence of extrapyramidal side effects, hyperprolactinemia, and sexual dysfunction was statistically significantly lower in olanzapine-treated than risperidone-treated patients. In addition, statistically significantly fewer adverse events were reported by olanzapine-treated patients than by their risperidone-treated counterparts. Thus, the differential preclinical profiles of these two drugs were also evident in a controlled, clinical investigation. Olanzapine seemed to have a risk-versus-benefit advantage.
Olanzapine is a potential new "atypical" antipsychotic agent. This double-blind, acute phase study compared two doses of olanzapine [1 mg/day (Olz1.0); 10 mg/day (Olz10.0)] with placebo in the treatment of 152 patients who met the DSM-III-R criteria for schizophrenia and had a Brief Psychiatric Rating Scale (BPRS)-total score (items scored 0-6) > or = 24. In overall symptomatology improvement [BPRS-total score and Positive and Negative Syndrome Scale (PANSS)-total score], Olz10.0 was statistically significantly superior to placebo. In positive symptom improvement (PANSS-positive score, BPRS-positive score), Olz10.0 was statistically significantly superior to placebo. In negative symptom improvement (PANSS-negative score), Olz10.0 was statistically superior to placebo. Olz 1.0 was clinically comparable to placebo in all efficacy comparisons. The only adverse event to show an overall statistically significant incidence difference was anorexia (reported for 10% of placebo-treated and 0% of Olz10.0-treated patients). The Olz10.0-treated patients improved over baseline with respect to parkinsonian and akathisia symptoms, and these changes were comparable with those observed with placebo. There were no dystonias associated with Olz10.0 treatment. At endpoint, the incidence of patients with elevated prolactin values did not differ statistically significantly between placebo-treated and Olz10.0-treated patients. Olanzapine appears to be not only safe and effective, but a promising atypical antipsychotic candidate.
Multicentre trials in patients with schizophrenia confirm that olanzapine is a novel antipsychotic agent with broad efficacy, eliciting a response in both the positive and negative symptoms of schizophrenia. Compared with traditional antipsychotic agents, olanzapine causes a lower incidence of extrapyramidal symptoms and minimal perturbation of prolactin levels. Generally, olanzapine is well tolerated. The pharmacokinetics of olanzapine are linear and dose-proportional within the approved dosage range. Its mean half-life in healthy individuals was 33 hours, ranging from 21 to 54 hours. The mean apparent plasma clearance was 26 L/h, ranging from 12 to 47 L/h. Smokers and men have a higher clearance of olanzapine than women and nonsmokers. After administering [14C]olanzapine, approximately 60% of the radioactivity was excreted in urine and 30% in faeces. Olanzapine is predominantly bound to albumin (90%) and alpha 1-acid glycoprotein (77%). Olanzapine is metabolised to its 10- and 4'-N-glucuronides, 4'-N-desmethylolanzapine [cytochrome P450 (CYP) 1A2] and olanzapine N-oxide (flavin mono-oxygenase 3). Metabolism to 2-hydroxymethylolanzapine via CYP2D6 is a minor pathway. The 10-N-glucuronide is the most abundant metabolite, but formation of 4'-N-desmethylolanzapine is correlated with the clearance of olanzapine. Olanzapine does not inhibit CYP isozymes. No clinically significant metabolic interactions were found between olanzapine and diazepam, alcohol (ethanol), imipramine, R/S-warfarin, aminophylline, biperiden, lithium or fluoxetine. Fluvoxamine, an inhibitor of CYP1A2, increases plasma concentrations of olanzapine; inducers of CYP1A2, including tobacco smoke and carbamazepine, decrease olanzapine concentrations. Orthostatic changes were observed when olanzapine and diazepam or alcohol were coadministered. Pharmacodynamic interactions occurred between olanzapine and alcohol, and olanzapine and imipramine, implying that patients should avoid operating hazardous equipment or driving an automobile while experiencing the short term effects of the combinations. Individual factors with the largest impact on olanzapine pharmacokinetics are gender and smoking status. The plasma clearance of olanzapine generally varies over a 4-fold range, but the variability in the clearance and concentration of olanzapine does not appear to be associated with the severity or duration of adverse effects or the degree of efficacy. Thus, dosage adjustments appear unnecessary for these individual factors. However, dosage modification should be considered for patients characterised by a combination of factors associated with decreased oxidative metabolism, for example, debilitated or elderly women who are nonsmokers.
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