From the Research
The lethal dose of propranolol is generally considered to be around 2 grams (2000 mg) or more in adults, although fatalities have occurred at lower doses. This is based on the most recent and highest quality study available, which investigated propranolol overdose and dose thresholds for severe toxicity 1. The study found that in patients who ingested only propranolol, the lowest reported dose for severe toxicity was 2,000 mg, and that 17 of 32 (53%) patients who ingested ≥2,000 mg had severe toxicity. Factors affecting lethality include the person's weight, tolerance, existing medical conditions, and whether other substances were taken simultaneously. Propranolol overdose is particularly dangerous because it blocks beta receptors in the heart and can cause severe bradycardia (slow heart rate), hypotension (low blood pressure), and cardiogenic shock.
Some key points to consider in the management of propranolol overdose include:
- The importance of immediate medical attention, as the window for effective intervention is limited
- The potential need for advanced interventions like cardiac pacing or extracorporeal membrane oxygenation in severe cases
- The use of gastric lavage, activated charcoal, intravenous fluids, atropine, and glucagon as part of the treatment regimen
- The potential for propranolol to cause seizures and central nervous system depression due to its lipophilic properties, which allow it to cross the blood-brain barrier.
It is also worth noting that the outcome of propranolol overdose is usually favorable with good supportive care, even in severe toxicity, as reported in the study by 1. However, the study also highlights the importance of prompt medical attention and the potential for severe toxicity, including cardiac arrest and death, at doses above 2,000 mg. Other studies, such as those reported in 2, 3, 4, and 5, also support the importance of prompt medical attention and the potential for severe toxicity in propranolol overdose, although they may not provide the same level of detail on dose thresholds as the study by 1.