Yes, Digoxin Overdose Causes Bradycardia
Digoxin overdose definitively causes bradycardia through multiple mechanisms, including severe sinus bradycardia, sinoatrial block, and various degrees of AV block, which can progress to complete heart block and asystole. 1, 2
Mechanism and Clinical Presentation
Digoxin slows sinoatrial and AV nodal conduction as part of its pharmacologic action. In overdose, this effect becomes pathologic and life-threatening. The 2023 American Heart Association guidelines explicitly state that patients with cardiac glycoside poisoning develop "cardiac conduction abnormalities, including atrioventricular nodal block" along with the potential for ventricular tachycardia, ventricular fibrillation, and asystole 1.
The FDA drug label confirms that digoxin "commonly prolongs the PR interval" and may cause:
- Severe sinus bradycardia or sinoatrial block in patients with pre-existing sinus node disease
- Advanced or complete heart block in patients with pre-existing incomplete AV block
- Various rhythm disturbances at high doses including first-degree, second-degree (Wenckebach), or third-degree heart block (including asystole) 2
Age-Specific Manifestations
In infants and children, bradycardia is often the earliest and most frequent manifestation of digoxin overdose, unlike adults where gastrointestinal and CNS symptoms may appear first. Sinus bradycardia in pediatric patients should be considered a sign of impending digoxin intoxication, especially in the absence of first-degree heart block 2.
Critical Clinical Caveat
Bradycardia from digoxin toxicity can occur even at therapeutic serum digoxin concentrations 3. A 2025 case report demonstrated severe digoxin toxicity with bradycardia and hyperkalemia at a serum level of only 1.4 ng/ml (within therapeutic range), which resolved after administration of digoxin-specific antibody fragments. This underscores that clinical features, not serum levels alone, should guide diagnosis and treatment decisions 3.
Recent case reports from 2024-2026 consistently document bradycardia as a presenting feature of digoxin toxicity, including cases with complete heart block, syncope, and BRASH syndrome (Bradycardia, Renal failure, AV-nodal blockade, Shock, and Hyperkalemia) 4, 5, 6.
Management Approach
When bradycardia from digoxin toxicity is identified:
Administer digoxin-specific antibody fragments (digoxin-Fab) - Class I recommendation for digoxin/digitoxin poisoning with 50-90% response rates and dysrhythmia resolution in 30-45 minutes 1
Consider atropine for symptomatic bradydysrhythmias - Class 2b recommendation, though evidence is limited to case reports with variable effects 1
Electrical pacing may be attempted as temporizing therapy, though complications are common (36% in one series) and some patients require higher-than-normal current 1
Do NOT use hemodialysis or other extracorporeal treatments - Class III (no benefit) recommendation due to digoxin's large volume of distribution 1