Off-label Clinical Applications of Olanzapine: A Narrative Review of Mechanisms, Efficacy and Safety

Abstract

Introduction: Off-label prescribing refers to the use of approved medications for indications, populations, dosages, or routes not formally approved by regulatory authorities. While legally permitted and often necessary in clinical practice, such use requires careful evaluation of safety and efficacy. Olanzapine, a second-generation atypical antipsychotic primarily approved for schizophrenia and bipolar I disorder, possesses a broad multi-receptor antagonism profile that may explain its increasing off-label clinical applications. Objective: To review the current evidence regarding major off-label clinical uses of olanzapine, including its mechanisms of action, therapeutic efficacy, and safety considerations. Methods: This review synthesizes findings from published literature, including randomized controlled trials, systematic reviews, meta-analyses, and observational studies evaluating off-label uses of olanzapine across different clinical conditions. Evidence was examined to identify therapeutic benefits, mechanisms of action, and reported adverse effects. Literature was sourced from databases such as PubMed, Scopus and Google Scholar. Results: Olanzapine has demonstrated significant benefit in several off-label indications. The strongest evidence exists for chemotherapy-induced nausea and vomiting (CINV), where its multi-receptor antagonism (dopamine, serotonin, histamine, muscarinic, and α-adrenergic receptors) contributes to effective antiemetic activity and has led to its inclusion in international antiemetic guidelines. Additional evidence supports its use in anorexia nervosa, where it may promote weight gain and reduce anxiety related to body image; insomnia, due to potent sedative effects mediated primarily by H1 and 5-HT2 receptor blockade and substance use disorders, where modulation of mesolimbic dopamine pathways may reduce craving and drug-seeking behaviour. Potential benefits have also been reported in pain syndromes, delirium, and anxiety-related conditions, although the strength of evidence varies and remains inconsistent in some indications. Across studies, common adverse effects include sedation and metabolic changes such as weight gain, while serious but rare events include QTc prolongation, neutropenia, and seizures. Conclusion: Olanzapine’s broad pharmacodynamic profile enables therapeutic benefits across multiple off-label indications, particularly when standard treatments fail. However, the risk of metabolic and sedative adverse effects necessitates careful patient selection and individualized risk–benefit assessment. Further large-scale randomized controlled trials are required to establish standardized dosing strategies and long-term safety for these off-label applications.