Treatment of Bradycardia Induced by Beta-Blockers or Calcium Channel Blockers

Introduction to Glucagon Therapy

The American College of Cardiology, American Heart Association, and Heart Rhythm Society recommend glucagon as a reasonable treatment for symptomatic or hemodynamically compromised bradycardia due to beta-blocker or calcium channel blocker overdose, with a Class IIa recommendation and level of evidence C-LD 1, 2, 3

Glucagon activates hepatic adenylate cyclase, producing positive inotropic and chronotropic effects that counteract the effects of beta-blockers, making it a reasonable treatment for bradycardia associated with beta-blocker or calcium channel blocker overdose 1, 2, 3
This mechanism is independent of beta-adrenergic receptors, allowing glucagon to function even when these receptors are completely blocked by beta-blockers 1, 2, 3

The American College of Cardiology recommends glucagon as a first-line therapy for beta-blocker overdose, with a dose of 3-10 mg IV administered over 3-5 minutes, followed by a continuous infusion of 3-5 mg/hour if necessary 1, 2, 3, 4
For calcium channel blocker overdose, calcium IV (1-2 g of 10% calcium chloride every 10-20 minutes) is the first-line treatment, but glucagon is also reasonable 1, 2, 3

If bradycardia persists despite glucagon, high-dose insulin therapy may be considered, with a bolus of 1 unit/kg followed by an infusion of 0.5-1 unit/kg/hour, along with concurrent dextrose administration 1, 2, 3, 4, 5
In refractory cases, vasopressors/inotropics (such as epinephrine 2-10 mcg/min or dopamine 5-20 mcg/kg/min) or temporary cardiac pacing may be necessary 4, 6, 5

The evidence for glucagon use in beta-blocker or calcium channel blocker overdose is primarily based on case reports and series, with limited controlled clinical trials 1, 2, 3
Glucagon has been shown to increase heart rate and cardiac output in animal models of beta-blocker and calcium channel blocker overdose, although the effects are often transient 1, 2, 3

The main side effects of glucagon are nausea and vomiting, which can be particularly concerning when airway protection is compromised 1, 2, 3
Other adverse effects include hypokalemia and hyperglycemia 4, 5

Continuous cardiac monitoring, frequent blood pressure measurements, and regular assessment of mental status and peripheral perfusion are necessary during glucagon therapy 4, 6, 5
Glucose and potassium levels should be monitored, especially when using high-dose insulin therapy 4, 5
Beta-blocker and calcium channel blocker toxicity can be fatal due to profound negative chronotropic and inotropic effects, as well as vasodilation, and may require presor adrenergic support 1, 2, 3

The American Heart Association recommends intravenous calcium as a reasonable treatment (Class IIa recommendation) for symptomatic or hemodynamically compromised bradycardia due to calcium channel blocker toxicity, with calcium gluconate preferred for peripheral IV administration to minimize vein irritation 7, 8, 9, 10
The American College of Cardiology suggests that both calcium chloride and calcium gluconate are commonly used, with calcium chloride providing more rapid increases in ionized calcium and preferred in critically ill patients when central access is available 7, 8, 10, 11
For pediatrics, the American Academy of Pediatrics recommends a dose of 20 mg/kg calcium chloride or 60 mg/kg calcium gluconate for calcium channel blocker toxicity, administered slowly with cardiac monitoring, and repeated as needed for clinical effect 11, 12

The American Heart Association indicates that calcium gluconate or chloride is also used for bradycardia caused by hypocalcemia, hyperkalemia with ECG changes, and hypermagnesemia causing cardiac conduction abnormalities 11, 12

The American College of Cardiology advises against confusing calcium channel blocker toxicity with beta-blocker toxicity, as glucagon is the first-line agent for beta-blocker overdose, not calcium 7, 8, 9, 10
The American Heart Association warns against mixing calcium with sodium bicarbonate or vasoactive amines, as they are incompatible in solution, and to monitor for extravasation, as calcium can cause severe tissue necrosis if it infiltrates peripheral tissues 11, 12

The American College of Cardiology suggests that high-dose insulin therapy and glucagon are reasonable alternative therapies for calcium channel blocker toxicity if bradycardia persists despite calcium administration 7, 8, 9, 10