IV Digoxin Dosing for Rate Control in Atrial Fibrillation When Beta Blockers Fail
Administer digoxin 0.25 mg IV every 2 hours up to a maximum total loading dose of 1.5 mg over 24 hours, followed by maintenance dosing of 0.125 to 0.375 mg daily IV or orally. 1, 2
Loading Dose Protocol
For adults requiring rapid rate control when beta blockers are ineffective:
- Initial dose: 0.25 mg IV administered over at least 5 minutes 1, 2
- Subsequent doses: 0.25 mg IV every 2 hours as needed 1
- Maximum total loading dose: 1.5 mg over 24 hours 1, 2
- Onset of action: 60 minutes or more 1
The FDA-approved loading regimen for adults and pediatric patients over 10 years is 8-12 mcg/kg total IV loading dose, with half administered initially, then ¼ of the loading dose every 6-8 hours twice 2. However, the practical guideline-based approach of 0.25 mg increments is more commonly used in clinical practice 1.
Administration Technique
Critical administration details to prevent complications:
- Administer each dose over at least 5 minutes to avoid systemic and coronary vasoconstriction 2
- Never give as bolus 2
- Can be given undiluted or diluted with at least 4-fold volume of sterile water, 0.9% saline, or 5% dextrose 2
- Avoid mixing with other drugs in the same container or IV line 2
Maintenance Dosing
After achieving rate control with loading doses:
- Maintenance dose: 0.125 to 0.375 mg daily IV or orally 1
- Adjust based on renal function, lean body weight, and clinical response 2
- For adults with normal renal function: 2.4-3.6 mcg/kg/day (given once daily) 2
Clinical Context and Recommendations
Digoxin has Class I, Level of Evidence B recommendation for IV rate control in atrial fibrillation 1, but important caveats exist:
When to Use Digoxin as Add-On Therapy:
- Heart failure with reduced ejection fraction: IV digoxin or amiodarone is recommended to control heart rate acutely in the absence of pre-excitation (Class I, Level B) 1
- Combination therapy: Digoxin combined with beta blockers or calcium channel blockers is reasonable for controlling both rest and exercise heart rate (Class IIa, Level B) 1
- Hemodynamically stable patients: When beta blockers alone are insufficient 1
Important Limitations:
Digoxin is relatively ineffective as monotherapy for rate control during exercise 3, 4, 5. It works primarily by enhancing vagal tone, making it most effective at rest 3, 5. The onset of action is slower (60+ minutes) compared to IV beta blockers (5 minutes) or calcium channel blockers (2-7 minutes) 1.
Alternative Considerations Before Digoxin
Before adding digoxin, consider these alternatives with faster onset:
- IV diltiazem: 0.25 mg/kg over 2 minutes, then 5-15 mg/h infusion (onset 2-7 minutes) 1
- IV verapamil: 0.075-0.15 mg/kg over 2 minutes (onset 3-5 minutes) 1
- IV amiodarone: 150 mg over 10 minutes for critically ill patients (Class IIa, Level B) 1
These agents have Class I recommendations and faster onset than digoxin 1.
Critical Safety Warnings
Absolute contraindications and precautions:
- DO NOT use in pre-excited atrial fibrillation (WPW syndrome) - potentially harmful (Class III: Harm, Level B) 1
- Monitor for digitalis toxicity (narrow therapeutic window) 1, 2
- Adjust dose for renal impairment 2
- Consider interruption or dose reduction before electrical cardioversion 2
- Major side effects: digitalis toxicity, heart block, bradycardia 1
Monitoring
Essential monitoring parameters: