Beta-Blocker Overdose

The most toxic beta-blocker is propranolol

• It competitively blocks beta-1- and beta-2-adrenoceptors

• Has direct membrane-depressant and CNS effects

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 is clinical

Routine toxicology screening does not usually include β-blockers

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