Can a patient with bradycardia (abnormally slow heart rate) take glucagon and hydralazine to raise their heart rate?

No, Glucagon and Hydralazine Should Not Be Used Together to Raise Heart Rate in Bradycardia

This combination is pharmacologically inappropriate and potentially dangerous—glucagon can increase heart rate in specific contexts (beta-blocker/calcium channel blocker overdose), while hydralazine typically causes reflex tachycardia but is not indicated for bradycardia treatment.

Why This Combination Is Problematic

Glucagon's Role in Bradycardia

Glucagon is specifically indicated for bradycardia caused by beta-blocker or calcium channel blocker overdose, not for general bradycardia management. 1

• The 2019 ACC/AHA/HRS Bradycardia Guidelines recommend glucagon (3-10 mg IV bolus followed by 3-5 mg/h infusion) specifically for beta-blocker or calcium channel blocker overdose causing symptomatic bradycardia (Class IIa, Level C-LD) 1
• Glucagon works by bypassing beta-receptors to increase cardiac contractility and heart rate through direct myocardial effects 1
• Critical warning: Glucagon may increase myocardial oxygen demand, blood pressure, and pulse rate, which may be life-threatening in patients with cardiac disease 2
• Glucagon can cause substantial increases in blood pressure and heart rate, requiring cardiac monitoring 2

Hydralazine's Inappropriate Use for Bradycardia

Hydralazine is a vasodilator that causes reflex tachycardia as a side effect, not a therapeutic agent for bradycardia. 1

• While one small 1981 study showed hydralazine increased heart rate in 21 patients with symptomatic sinus bradycardia 3, this has never been validated in modern guidelines or larger trials
• The 2018 ACC/AHA Hypertension Guidelines explicitly state: "BP begins to decrease within 10-30 min, and the fall lasts 2-4 h. Unpredictability of response and prolonged duration of action do not make hydralazine a desirable first-line agent for acute treatment in most patients" 1
• Hydralazine causes reflex tachycardia and fluid retention, which is why it requires concurrent beta-blocker and diuretic therapy when used in heart failure 4, 5

Dangerous Drug Interaction Potential

Combining glucagon (which increases heart rate and blood pressure) with hydralazine (which causes unpredictable blood pressure responses) creates significant hemodynamic instability risk. 2, 1

• Glucagon may cause transient increases in pulse and blood pressure, especially in patients taking beta-blockers 2
• Hydralazine has unpredictable blood pressure responses and prolonged duration of action (2-4 hours) 1
• The combination could result in severe hypotension, excessive tachycardia, or paradoxical hypertension 2, 6

Appropriate Management of Bradycardia

First-Line Acute Management

For symptomatic bradycardia, atropine 0.5-1 mg IV (repeated every 3-5 minutes to maximum 3 mg) is the first-line agent. 1

• Atropine is reasonable to increase sinus rate in patients with sinus node dysfunction associated with symptoms or hemodynamic compromise (Class IIa, Level C-LD) 1
• Critical exception: Atropine should NOT be used in heart transplant patients without autonomic reinnervation (Class III: Harm) 1

Second-Line Agents for Refractory Bradycardia

If atropine is ineffective, beta-agonists (dopamine, isoproterenol, dobutamine, or epinephrine) may be considered in patients at low likelihood of coronary ischemia (Class IIb, Level C-LD). 1

• Dopamine: 5-20 mcg/kg/min IV, starting at 5 mcg/kg/min and increasing by 5 mcg/kg/min every 2 minutes 1
• Isoproterenol: 20-60 mcg IV bolus or infusion of 1-20 mcg/min based on heart rate response 1
• Epinephrine: 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV titrated to desired effect 1
• Monitor for potential ischemic chest pain and arrhythmias, especially with dopamine doses >20 mcg/kg/min 1

Specific Scenarios Requiring Alternative Agents

For beta-blocker or calcium channel blocker overdose causing bradycardia, glucagon is the appropriate choice. 1

• Glucagon 3-10 mg IV bolus followed by infusion of 3-5 mg/h (Class IIa, Level C-LD) 1
• Calcium chloride 10% (1-2 g IV every 10-20 minutes) or calcium gluconate 10% (3-6 g IV every 10-20 minutes) for calcium channel blocker overdose 1
• High-dose insulin therapy (1 unit/kg IV bolus followed by 0.5 units/kg/h infusion) for beta-blocker or calcium channel blocker overdose 1

Definitive Management

Evaluation and treatment of reversible causes is mandatory before considering permanent pacing. 1

• Common reversible causes include medications (beta-blockers, calcium channel blockers, digoxin), electrolyte abnormalities (hyperkalemia), hypothyroidism, hypothermia, and acute myocardial infarction 1
• Temporary transcutaneous or transvenous pacing may be necessary for hemodynamically unstable patients 1
• Permanent pacemaker placement is the definitive treatment for chronic symptomatic bradycardia without reversible causes 1

Critical Pitfalls to Avoid

• Never use glucagon for general bradycardia—it is specifically for beta-blocker/calcium channel blocker overdose 1, 2
• Never use hydralazine as a primary agent to increase heart rate—its effects are unpredictable and it is not guideline-recommended for this indication 1, 3
• Never combine agents with opposing or unpredictable hemodynamic effects without clear guideline support 2, 6
• Always identify and treat reversible causes before escalating to advanced therapies 1
• Monitor cardiac rhythm, blood pressure, and heart rate continuously during acute bradycardia management 1, 2