Short communication 183 Olanzapine overdose: a series of analytically confirmed cases Mary Morgan b , L. Peter Hackett a and Geoffrey K. Isbister c To describe the spectrum of clinical effects in olanzapine overdose and investigate the factors that predict severe outcomes. We analysed olanzapine-overdose events confirmed by drug analysis. Demographic, clinical and outcome data were recorded for each presentation. The relationship between dose and therapeutic olanzapine use, and outcomes (length of hospital stay, intensive care unit admission, mechanical ventilation, Glasgow coma score < 9 and delirium) were investigated. Thirty-seven olanzapine overdose admissions were included. Median age was 30 years (interquartile range: 24–40 years), 24 women and 27 taking olanzapine therapeutically. Median ingested dose was 150 mg (range: 10–1600 mg). Olanzapine overdose was characterized by tachycardia (73%), central nervous system depression (43%), miosis (39%) and delirium (54%), which were either present on admission or developed within 6 h. There was no relationship between the dose and length of hospital stay, intensive care unit admission, Glasgow coma score < 9 or delirium, but there was a trend towards more severe outcomes in patients not taking olanzapine therapeutically. Patients with delirium had an increased length of hospital stay and intensive care unit admission rate (50%) and 70% of them required physical or chemical restraint. Olanzapine overdose causes a high rate of delirium and central nervous system sedation that requires significant inpatient resources. Olanzapine overdoses should be initially observed for 6 h and patients not taking olanzapine regularly may have more severe effects. Int Clin Psychopharmacol 22:183–186  c 2007 Lippincott Williams & Wilkins. International Clinical Psychopharmacology 2007, 22:183–186 Keywords: antipsychotic overdose, delirium, olanzapine, overdose, toxicity a Clinical Pharmacology and Toxicology, PathWest Laboratory Medicine WA, Perth, b John Hunter Hospital and c Newcastle Mater Hospital and Conjoint Senior Lecturer, Discipline of Clinical Pharmacology, University of Newcastle, Newcastle, Australia Correspondence to Geoffrey K. Isbister, Department of Clinical Toxicology, Newcastle Mater Hospital, Edith St, Waratah NSW 2298, Australia Tel: + 612 4921 1211; fax: + 612 4921 1870; e-mail: gsbite@ferntree.com Received 15 August 2006 Accepted 21 December 2006 Introduction Olanzapine is an atypical antipsychotic drug of the thienobenzodiazepine class, introduced in the mid- 1990s for the treatment of schizophrenia and moderate to severe manic episodes (Trenton et al., 2003). It has an improved tolerability profile compared with traditional antipsychotics with less extrapyramidal side effects (Fogel and Dı ´az, 1998). The major problem in therapeu- tic doses is weight gain (Roerig et al., 2005) and insulin resistance (Gianfrancesco et al., 2002; Meatherall and Younes, 2002; Courvoisie et al., 2004). Most reports of olanzapine overdose are case reports and small cases series (Elian, 1998; Fogel and Dı ´az, 1998; Cohen et al., 1999; O’Malley et al., 1999; Gerber and Cawthon, 2000; Burns, 2001; Mazzola et al., 2003; Trenton et al., 2003; Weizberg et al., 2006). Olanzapine overdose is character- ized by central nervous system (CNS) depression of varying severity, delirium and agitation, tachycardia and miosis (O’Malley et al., 1999). These patients are often described as being sedated with an underlying anti- cholinergic delirium (Palenzona et al., 2004). We present a single-centre case series of olanzapine overdoses to describe the spectrum of clinical effects, investigate factors that predict intensive care unit (ICU) admission and length of stay, and to further define the frequency and the severity of delirium. Methods All the patients presenting to a tertiary toxicology unit between December 2000 and September 2003 and reporting an olanzapine overdose were eligible for inclusion. Blood was collected for olanzapine quantifica- tion. The study had institutional ethics approval. The data collected were patient demographics (age, sex), details of the overdose (time of overdose, ingested amount, coingestants and therapeutic use of olanzapine), clinical features on admission [heart rate, blood pressure, temperature, pupil size and Glasgow coma score (GCS)], serial measurements of GCS, blood pressure, heart rate and temperature, complications (seizures, arrhythmias, hypotension, coma and rhabdomyolysis), investigations (ECG including QRS and QT), ICU admission, mechan- ical ventilation, length of hospital stay (LOS), any description of delirium and treatment (including use and duration of sedation and mechanical restraints). Additional information was extracted from the medical records about the presence of delirium or the use of sedation alone, based on the use of predefined key words: ‘delirium’, ‘agitated’, ‘hyperstimulated’, ‘confusion’ and ‘restless’ or ‘drowsy’ and ‘sedated’. Olanzapine assays were performed by high-performance liquid chromatography and UV detection. Accurate quantification of olanzapine in blood was not possible 0268-1315  c 2007 Lippincott Williams & Wilkins Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.