What is the recommended dose of digoxin (digitalis glycoside) for treating atrial fibrillation (afib)?

Digoxin Dosing for Atrial Fibrillation

For atrial fibrillation, digoxin should be dosed at 0.125 to 0.25 mg daily, targeting serum concentrations of 0.5 to 1.0 ng/mL. 1

Initial Dosing Strategy

• Standard dosing: 0.125-0.25 mg daily for most patients 1
• Lower dosing (0.125 mg daily or every other day) recommended for:
  • Patients >70 years old
  • Patients with impaired renal function
  • Patients with low lean body mass 1

Important Considerations

Target Serum Concentrations

• Aim for serum digoxin levels between 0.5-1.0 ng/mL 1
• Levels >1.0 ng/mL have not shown superior outcomes 1
• Levels >2.0 ng/mL are associated with toxicity 1

Loading Doses

• Loading doses are not recommended for chronic AF management 1
• No clinical benefit to using loading doses in heart failure patients with AF 1

Role in AF Management

• Digoxin is not recommended as primary therapy for acute AF with rapid ventricular response 1
• In AF, digoxin should be considered as an adjunctive agent for rate control 1
• Beta-blockers or calcium channel blockers are usually more effective for rate control, particularly during exercise 1

Special Situations

Concomitant Heart Failure

• Digoxin can be particularly useful in patients with both AF and heart failure 2
• When used for AF with heart failure, digoxin provides positive inotropic support while controlling rate 2

Drug Interactions

• Reduce digoxin dose when used with:
  • Amiodarone
  • Verapamil
  • Quinidine
  • Clarithromycin
  • Erythromycin
  • Itraconazole
  • Cyclosporine 1

Monitoring and Safety

Risk Factors for Toxicity

• Hypokalemia
• Hypomagnesemia
• Hypothyroidism
• Hypercalcemia
• Renal impairment 1, 3

Signs of Toxicity

• Cardiac arrhythmias (ectopic beats, heart block)
• Gastrointestinal symptoms (anorexia, nausea, vomiting)
• Neurological complaints (visual disturbances, disorientation, confusion) 1

Cautions and Contraindications

• Avoid in patients with significant sinus or atrioventricular block without a pacemaker 1
• Use cautiously in patients taking other drugs that affect AV nodal function 1
• Recent evidence suggests potential increased mortality in AF patients on digoxin, indicating the need for careful patient selection 4

Practical Algorithm for Digoxin Use in AF

1. Determine if patient has contraindications to digoxin
2. For most patients, start with 0.125 mg daily
3. For elderly, renal impairment, or low body mass, use 0.125 mg daily or every other day
4. Target serum concentration: 0.5-1.0 ng/mL
5. Monitor for signs of toxicity, especially with concomitant medications or electrolyte abnormalities
6. Consider adding a beta-blocker for improved rate control, particularly for exercise-related tachycardia

Remember that digoxin is generally more effective for controlling resting heart rate than exercise heart rate in AF patients 1, and should typically be considered as an adjunctive therapy rather than first-line treatment unless heart failure is present.