Glucagon Dosing for Bradycardia
For bradycardia due to beta-blocker or calcium channel blocker overdose, administer glucagon 3-10 mg IV bolus followed by a continuous infusion of 3-5 mg/hour. 1
Clinical Context and Indication
Glucagon is specifically indicated for symptomatic bradycardia with hemodynamic compromise caused by beta-blocker or calcium channel blocker toxicity. 1 The ACC/AHA/HRS guidelines give this a Class IIa recommendation (reasonable therapy) with Level C-LD evidence. 1, 2
Dosing Protocol
Initial Bolus Dose
- Administer 3-10 mg IV over 3-5 minutes 1, 2
- This range allows titration based on patient size and severity of toxicity 2
Maintenance Infusion
- Follow immediately with continuous infusion of 3-5 mg/hour 1, 2
- The infusion is essential because glucagon has transient effects with rapid metabolism 2
- Clinical improvement typically occurs within 5-10 minutes of administration 3
Mechanism and Rationale
Glucagon bypasses blocked beta-adrenergic receptors by directly activating hepatic adenylate cyclase, which increases myocardial contractility and heart rate independent of beta-receptor stimulation. 2, 4 This makes it uniquely effective when standard therapies like atropine fail in beta-blocker toxicity. 3, 5
Monitoring Requirements
- Monitor glucose and potassium levels continuously during therapy 1, 2
- Maintain continuous cardiac monitoring to assess treatment response 2
- Watch for side effects including nausea, vomiting, hypokalemia, and hyperglycemia 4
Alternative and Adjunctive Therapies
If glucagon alone is insufficient:
- High-dose insulin therapy: 1 unit/kg IV bolus followed by 0.5 units/kg/hour infusion (Class I recommendation for refractory cases) 1, 2
- Intravenous calcium (for calcium channel blocker overdose specifically): 1-2 g of 10% calcium chloride every 10-20 minutes or infusion of 0.2-0.4 mL/kg/hour 1, 2
- Vasopressors may be initiated immediately for hypotension 2
Important Caveats
Glucagon is NOT indicated for bradycardia from other causes such as primary sinus node dysfunction, vagally-mediated bradycardia, or digoxin toxicity—these require different management approaches. 1 For non-overdose bradycardia, atropine (0.5-1 mg IV) remains the first-line agent. 1
The high cost and limited availability of glucagon in some settings may be practical limitations, but its efficacy in beta-blocker toxicity makes it essential to have available. 4