Medications That Can Cause Bradycardia
Several medication classes can cause bradycardia, with beta-blockers, calcium channel blockers, and digoxin being the most common culprits. 1, 2 Understanding these medications is essential for preventing, recognizing, and managing drug-induced bradycardia.
Common Medication Classes That Cause Bradycardia
Beta-Blockers
- Metoprolol, atenolol, propranolol, esmolol, and labetalol 1
- Mechanism: Antagonize sympathetic tone in nodal tissue, slowing conduction
- Can cause significant bradycardia, especially when combined with other negative chronotropic agents
- Carvedilol has additional alpha-blocking properties that can worsen hypotension 1
- Sotalol has additional Class III antiarrhythmic effects 3
Calcium Channel Blockers
- Non-dihydropyridines: Diltiazem, verapamil 1, 4
- Mechanism: Block calcium channels in cardiac conduction tissue
- Severe bradyarrhythmias may occur with usual doses in sensitive individuals 1
- Risk increases significantly when combined with beta-blockers 5
Cardiac Glycosides
- Digoxin 1
- Mechanism: Inhibits sodium-potassium ATPase, increases vagal tone
- Bradycardia is a common and desired pharmacological effect but can become excessive 1
- Toxicity risk increases with renal dysfunction or drug interactions
Other Medications
- Antiarrhythmic drugs:
- Cholinesterase inhibitors: Donepezil 6
- Centrally-acting agents: Clonidine 1, 4
- Ivabradine: Direct If current inhibitor 7, 4
High-Risk Combinations
Beta-blockers + calcium channel blockers: This combination can cause profound bradycardia and heart block 1, 5
Beta-blockers + digoxin: Both slow AV conduction and decrease heart rate 3
Calcium channel blockers + digoxin: Diltiazem and verapamil can increase digoxin levels by 50-75% during the first week of therapy 4
Multiple antiarrhythmic agents: Combinations can have additive effects on cardiac conduction 1
Beta-blockers + clonidine: Sinus bradycardia requiring hospitalization and pacemaker insertion has been reported 4
Risk Factors for Drug-Induced Bradycardia
- Advanced age (>70 years) 5
- Pre-existing cardiac disease
- Renal or hepatic dysfunction 7, 4
- Electrolyte abnormalities
- Concomitant use of multiple bradycardia-inducing medications
- Overdose situations 8
Management of Drug-Induced Bradycardia
Asymptomatic Bradycardia
- Monitor closely but no immediate intervention required 2
- Consider dose reduction of offending medication
Symptomatic Bradycardia
- Discontinue or reduce dose of the offending medication 1
- First-line pharmacologic therapy: Atropine 0.5-1 mg IV every 3-5 minutes (maximum 3 mg) 2
- Second-line options if atropine ineffective:
- Temporary pacing for refractory cases 2
- For specific toxicities:
Prevention Strategies
- Avoid combining multiple bradycardia-inducing medications when possible 1
- When beta-blockers and calcium channel blockers must be used together, administer at different times of day 1
- Monitor heart rate and blood pressure regularly in patients on these medications
- Adjust doses appropriately in elderly patients and those with renal or hepatic impairment 7, 4
- Be vigilant for drug interactions that can increase levels of bradycardia-inducing drugs 4
Important Cautions
- Bradycardia may develop even months after starting medications, particularly with combinations of beta-blockers and sodium channel blockers 5
- Abrupt withdrawal of beta-blockers can lead to clinical deterioration and should be avoided 1
- When treating bradycardia, consider the possibility of drug interactions before adding additional medications 1
- Patients with less physiologic reserve (low BMI, elderly) may have less tolerance for bradycardia 2