A prospective study of acute propranolol overdose defining dose thresholds of severe toxicity (ATOM – 9)

Propranolol is a beta-adrenoceptor blocking drug with sodium channel-blocking properties that can cause life-threatening toxicity in overdose. Limited research defines dose thresholds of toxicity. We aimed to investigate propranolol overdose and dose thresholds for severe toxicity. This is a prospective series of patients with acute propranolol overdose ≥360 mg from August 2014 to December 2023 enrolled through the Australian TOxicology Monitoring (ATOM) collaboration. Severe toxicity was defined as seizure, coma, inotrope therapy, electrocardiographic evidence of sodium channel blockade, or cardiac arrest. There were 209 presentations in 165 patients (median age 30 years [range 15–80 years]; 117 females, 71%). The median reported dose ingested was 1,000 mg (IQR: 600–2,000 mg; range 360–16,000 mg). Co-ingestion occurred in 155 (74%) patients, most commonly involving benzodiazepines (n = 52). Bradycardia (heart rate Severe toxicity was common, occurring in a quarter of all propranolol overdoses and half of the isolated propranolol ingestions (≥2,000 mg). The outcome was usually favourable with good supportive care, even in severe toxicity. The dose threshold for severe toxicity in isolated propranolol overdose appeared to be 2,000 mg.