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There are a wide variety of beta-adrenergic blocking drugs, with varying pharmacologic and pharmacokinetic properties (see Table 11–9). The most toxic beta-blocker is propranolol, which not only blocks beta-1 and beta-2 adrenoceptors but also has direct membrane-depressant and central nervous system effects.
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The most common findings with mild or moderate intoxication are hypotension and bradycardia. Cardiac depression from more severe poisoning is often unresponsive to conventional therapy with beta-adrenergic stimulants such as dopamine and norepinephrine. In addition, with propranolol and other lipid-soluble drugs, seizures and coma may occur. Propranolol, oxprenolol, acebutolol, and alprenolol also have membrane-depressant effects and can cause conduction disturbance (wide QRS interval) similar to tricyclic antidepressant overdose.
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The diagnosis is based on typical clinical findings. Routine toxicology screening does not usually include beta-blockers.
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A. Emergency and Supportive Measures
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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.
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For drugs ingested within an hour of presentation (or longer after ingestion of an extended-release formulation), administer activated charcoal.
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For persistent bradycardia and hypotension, give glucagon, 5–10 mg intravenously, followed by an infusion of 1–5 mg/h. Glucagon is an inotropic agent that acts at a different receptor site and is therefore not affected by beta-blockade. 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.
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Graudins
A
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et al. Massive atenolol, lisinopril, and chlorthalidone overdose treated with endoscopic decontamination, hemodialysis, Impella percutaneous left ventricular assist device, and ECMO. J Med Toxicol. 2015 Mar;11(1):110–4.
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et al. Severe beta blocker and calcium channel blocker overdose: role of high dose insulin. Am J Emerg Med. 2018 Apr;36(4):736.e5–6.
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