What is the recommended dose of digoxin (digitalis glycoside) for a patient with atrial fibrillation (a fib)?

Digoxin Dosing in Atrial Fibrillation

For patients with atrial fibrillation, the recommended digoxin dosing is 0.125-0.25 mg daily for most adults with normal renal function, with lower doses (0.125 mg daily or every other day) for elderly patients over 70 years, those with impaired renal function, or low lean body mass. 1

Initial Dosing Strategy

Loading Dose (if needed for rapid rate control):

• IV administration: 0.25-0.5 mg IV bolus initially
• Can repeat 0.25 mg IV bolus up to maximum dose of 1.0 mg over 24 hours
• Maximum loading dose: 8-12 mcg/kg given at 6-8 hour intervals 2

Maintenance Dose:

• Standard maintenance dose: 0.125-0.25 mg daily 1, 3
• Dose should be based on:
  • Age (lower doses for patients >70 years)
  • Lean body weight
  • Renal function
  • Concomitant medications 2, 1

Dosing Adjustments Based on Patient Factors

Renal Function:

• For creatinine clearance <60 mL/min: Reduce dose to 0.125 mg daily 1
• Patients with renal impairment have 2.6 times higher odds of experiencing toxic levels 1

Age:

• Patients >70 years: 0.125 mg daily or every other day 1, 3

Body Weight:

• For a 70 kg patient with normal renal function: 0.25 mg daily 1
• Adjust based on lean body weight (not total body weight)

Monitoring and Target Levels

Serum Concentration:

• Target therapeutic range: 0.5-0.9 ng/mL 1
• Toxicity associated with levels >2.0 ng/mL 2, 3
• Check levels 6-24 hours after administration 1

Heart Rate Targets:

• Target heart rate: <80 bpm at rest, <110-120 bpm with exercise 1
• Assess rate control within 24 hours of loading dose 4

Important Precautions

Contraindications:

• Wolff-Parkinson-White (WPW) syndrome with AF
• AV block greater than first degree or SA node dysfunction (without pacemaker)
• Renal dysfunction (requires dose adjustment, not absolute contraindication) 2

Drug Interactions:

• Reduce digoxin dose by 30-50% when used with amiodarone 2
• Reduce digoxin dose by at least 50% when used with dronedarone 2
• Monitor digoxin levels when used with: verapamil, clarithromycin, cyclosporine, erythromycin, flecainide, itraconazole, posaconazole, propafenone, voriconazole 2

Clinical Considerations

• Digoxin is not effective for converting recent-onset AF to sinus rhythm 5
• For patients with AF and rapid ventricular response, high doses of digoxin (>0.25 mg daily) for rate control are not recommended 3
• When additional rate control is needed, consider adding a beta-blocker rather than increasing digoxin dose 3
• A large retrospective study suggested increased mortality risk in patients treated with digoxin for newly diagnosed AF; use with caution 2

Signs of Toxicity to Monitor

• Early signs: anorexia, nausea, vomiting, visual changes (seeing yellow halos)
• Cardiac arrhythmias can occur with toxicity
• Risk increases with hypokalemia, hypomagnesemia, or hypothyroidism 3

Remember that digoxin has a narrow therapeutic window, and careful dosing based on patient characteristics is essential to maximize efficacy while minimizing toxicity risk.