Treatment with olanzapine (like clozapine) may result in increased weight gain and increased glucose and cholesterol levels when compared to most other second-generation antipsychotic drugs used to treat schizophrenia. Comparison
The National Institute for Health and Care Excellence, the British Association for Psychopharmacology, and the World Federation of Societies for Biological Psychiatry suggest that little difference in effectiveness is seen between antipsychotics in prevention of relapse, and recommend that the specific choice of antipsychotic be chosen based on a persons preference and the drugs side-effect profile. The U.S. Agency for Healthcare Research and Quality concludes that olanzapine is not different from haloperidol in the treatment of positive symptoms and general psychopathology, or in overall assessment, but that it is superior for the treatment of negative and depressive symptoms. It has a lower risk of causing movement disorders than typical antipsychotics.In a 2013 comparison of fifteen antipsychotic drugs in schizophrenia, olanzapine was ranked third in efficacy. It was 5% more effective than risperidone (fourth), 24-27% more effective than haloperidol, quetiapine, and aripiprazole, and 33% less effective than clozapine (first). A 2013 review of first-episode schizophrenia concluded that olanzapine is superior to haloperidol in providing a lower discontinuation rate, and in short-term symptom reduction, response rate, negative symptoms, depression, cognitive function, discontinuation due to poor efficacy, and long-term relapse, but not in positive symptoms or on the clinical global impressions (CGI) score.
Metabolic effects
The US Food and Drug Administration (FDA) requires all atypical antipsychotics to include a warning about the risk of developing hyperglycemia and diabetes, both of which are factors in the metabolic syndrome. These effects may be related to the drugs ability to induce weight gain, although some reports have been made of metabolic changes in the absence of weight gain. Studies have indicated that olanzapine carries a greater risk of causing and exacerbating diabetes than another commonly prescribed atypical antipsychotic, risperidone. Of all the atypical antipsychotics, olanzapine is one of the most likely to induce weight gain based on various measures. The effect is dose dependent in humans and animal models of olanzapine-induced metabolic side effects. There are some case reports of olanzapine-induced diabetic ketoacidosis. Olanzapine may decrease insulin sensitivity, though one 3-week study seems to refute this. It may also increase triglyceride levels.Despite weight gain, a large multicenter, randomized National Institute of Mental Health study found that olanzapine was better at controlling symptoms because patients were more likely to remain on olanzapine than the other drugs. One small, open-label, nonrandomized study suggests that taking olanzapine by orally dissolving tablets may induce less weight gain, but this has not been substantiated in a blinded experimental setting. Post-injection delirium/sedation syndrome
Postinjection delirium/sedation syndrome (PDSS) is a rare syndrome that is specific to the long-acting injectable formulation of olanzapine, olanzapine pamoate. The incidence of PDSS with olanzapine pamoate is estimated to be 0.07% of administrations, and is unique among other second-generation, long-acting antipsychotics (e.g.