β-Blocker Overdose

Key Features

• The most toxic β-blocker is propranolol

  • It competitively blocks β₁- and β₂-adrenoceptors

  • Has direct membrane-depressant and CNS effects

Clinical Findings

• Hypotension and bradycardia are common with mild or moderate intoxication

• Cardiac depression from more severe poisoning is often unresponsive to conventional β-adrenergic stimulants such as dopamine and norepinephrine

• With propranolol and other lipid-soluble drugs, seizures and coma may occur

• Propranolol, oxprenolol, acebutolol, and alprenolol

  • Have membrane-depressant effects

  • Can cause conduction disturbance (wide QRS interval) similar to tricyclic antidepressant overdose

Diagnosis

• Diagnosis is clinical

• Routine toxicology screening does not usually include β-blockers

Treatment

• Activated charcoal

  • Administer 60–100 g orally or via gastric tube, mixed in aqueous slurry

  • Repeated doses may be given

• Attempts to treat bradycardia or heart block with atropine (0.5–2 mg intravenously), isoproterenol (2–20 mcg/min by intravenous infusion, titrated to the desired heart rate), or an external transcutaneous cardiac pacemaker are often ineffective, and specific antidotal treatment may be necessary

• For persistent bradycardia and hypotension, give glucagon, 5–10 mg intravenously, followed by infusion of 1–5 mg/h

• High-dose insulin (0.5–1 unit/kg/h intravenously) along with glucose supplementation has also been used to reverse severe cardiotoxicity

• Membrane-depressant effects (wide QRS interval) may respond to boluses of sodium bicarbonate (50–100 mEq intravenously) as for tricyclic antidepressant poisoning

• Intravenous lipid emulsion (Intralipid 20%, 1.5 mL/kg) has been used successfully in severe propranolol overdose

• Extracorporeal membrane oxygenation (ECMO) should be considered for refractory shock