Can digoxin (digitalis glycoside) be given 125 micrograms (mcg) and 67.5 mcg on alternate days?

Digoxin Alternating Dosage Schedule: 125 mcg and 67.5 mcg on Alternate Days

Yes, digoxin can be administered as 125 mcg and 67.5 mcg on alternate days, as this approach is consistent with guideline recommendations for lower dosing strategies in certain patient populations. 1

Rationale for Alternating Dosage

Digoxin has a narrow therapeutic index and a long half-life (40 hours in normal renal function, extending to over 100 hours in renal impairment), which makes alternating day dosing pharmacologically appropriate 2. This approach provides several benefits:

• Allows for a lower average daily dose while maintaining therapeutic effect
• Reduces risk of toxicity, particularly in vulnerable populations
• Achieves steady-state plasma concentrations in the recommended range of 0.5-0.9 ng/mL 1

Appropriate Patient Populations for This Regimen

This alternating dosing strategy is particularly appropriate for:

• Patients over 70 years of age 1
• Those with impaired renal function 1
• Patients with low lean body mass 1
• Those taking medications that may increase digoxin levels (amiodarone, verapamil, clarithromycin, erythromycin, itraconazole, cyclosporine, quinidine) 1

Guideline-Based Dosing Recommendations

Current guidelines support the use of lower doses of digoxin:

• The 2022 AHA/ACC/HFSA guideline specifically states: "Low doses (0.125 mg daily or every other day) should be used initially if the patient is >70 years of age" 1
• Doses of 0.125 to 0.25 mg daily are commonly recommended for maintenance therapy 1
• Higher doses (0.375-0.5 mg daily) are rarely needed or used 1

Monitoring Considerations

When implementing an alternating dosing schedule:

• Target serum digoxin concentrations of 0.5-0.9 ng/mL 1
• Higher concentrations (>1.0 ng/mL) have not been associated with superior outcomes and may increase mortality risk 1
• Monitor for signs of toxicity: cardiac arrhythmias, gastrointestinal symptoms, and neurological complaints 1
• Be vigilant for electrolyte abnormalities, particularly hypokalemia and hypomagnesemia, which can potentiate toxicity 1

Common Pitfalls to Avoid

1. Failure to adjust for drug interactions: Medications like amiodarone, verapamil, and certain antibiotics can significantly increase digoxin levels 1

2. Overlooking renal function: Digoxin's half-life can extend beyond 100 hours in renal failure, requiring dose adjustment 2

3. Ignoring age-related changes: Elderly patients have increased sensitivity to digoxin and often require lower doses 3

4. Inadequate monitoring: Regular assessment of serum levels is essential, especially after dosage changes or when starting interacting medications 3

5. Using interrupted dosing without careful monitoring: Interrupted dosing schedules show greater variability in drug levels compared to continuous dosing 4

The alternating day regimen of 125 mcg and 67.5 mcg provides an average daily dose of approximately 96 mcg, which falls within the lower recommended dosing range and is appropriate for many patients who require digoxin therapy while minimizing risk of toxicity.