Chlorpromazine overdose: a case series

Abstract

Introduction Chlorpromazine, one of the oldest antipsychotic medications, remains widely available and is still taken in overdose. We aimed to investigate the clinical effects of chlorpromazine overdose and determine if there is a relationship between the reported dose ingested and intensive care unit admission or endotracheal intubation. Methods We performed a retrospective analysis of patients admitted to our toxicology tertiary referral hospital with chlorpromazine overdose (reported dose ingested greater than 300 mg) between 1987 and 2023. We extracted demographic information, details of ingestion, clinical effects and complications (Glasgow Coma Scale, hypotension [systolic blood pressure less than 90 mmHg], delirium, dysrhythmias), length of stay, intensive care unit admission, and endotracheal intubation. Results There were 218 chlorpromazine overdose cases, with presentations decreasing in frequency over the 36 years. The median age at presentation was 32 years (interquartile range: 25–40 years) and 143 (61 per cent) were female. The median reported dose ingested was 1,250 mg (interquartile range; 700–2,500 mg). The majority of presentations (135; 62 per cent) involved reported co-ingestion of other medications, typically benzodiazepines, paracetamol or antipsychotics. There were 76 (35 per cent) chlorpromazine alone ingestions in which there was a slightly higher median reported dose ingested of 1,650 mg (interquartile range: 763–3,000 mg) compared to the reported co-ingestion group, median reported dose ingested of 1,200 mg (interquartile range: 700–2,100 mg). Of all presentations, 36 (27 per cent) had a Glasgow Coma Scale less than 9, 50 (23 per cent) were admitted to the intensive care unit, and 32 (15 per cent) were endotracheally intubated. There was a significant difference in the median reported dose ingested between patients intubated (2,000 mg; interquartile range: 1,388–3,375 mg) and those not intubated (1,200 mg; interquartile range: 644–2,050mg; P < 0.001), and between those admitted to the intensive care unit and not admitted to the intensive care unit (P < 0.0001). The median reported dose ingested in seven chlorpromazine alone presentations who were intubated was 2,500 mg (interquartile range: 2,000–8,000 mg, range: 1,800–20,000 mg). Eighteen (8 per cent) patients developed delirium, eight (4 per cent) had hypotension, three had seizures, and there was one death. Discussion Almost one quarter of cases were admitted to the intensive care unit and over half of these were intubated. Whist the decision to admit to an intensive care unit or intubate a patient is based on clinical need, there was a significant association between reported dose ingested and requirement for endotracheal intubation. Both the frequency of presentation and reported dose ingested declined after 2013. The major limitations of the study were a retrospective design and no analytical confirmation of ingestion. Conclusions We found that the most common effect of chlorpromazine overdose was central nervous system depression and that endotracheal intubation was associated with larger reported doses ingested, particularly in single chlorpromazine ingestions.