Digoxin Dosing Interval
For maintenance therapy, digoxin should be administered once daily, with repeat doses given at 24-hour intervals. 1
Loading Dose Intervals (When Rapid Digitalization Required)
When loading doses are necessary for urgent situations, additional fractions of the loading dose may be given at 6-8 hour intervals, with careful clinical assessment before each subsequent dose. 2, 3, 1
Specific Loading Protocol:
- Initial IV bolus: 0.25-0.5 mg 2, 3
- Repeat doses: 0.25 mg can be repeated at 6-8 hour intervals 2, 3, 2
- Maximum loading dose: 1.0 mg over 24 hours (8-12 mcg/kg) 2, 3, 1
- Oral loading: Additional doses of 0.125-0.375 mg may be given at 6-8 hour intervals until adequate clinical effect 1
Critical Caveat About Loading:
Loading doses should be reserved only for hemodynamically unstable supraventricular tachycardia or atrial fibrillation with rapid ventricular rate causing acute decompensation—the American College of Cardiology recommends starting directly with maintenance dosing in most situations unless rapid digitalization is urgently needed. 4
Maintenance Dosing Schedule
Once maintenance therapy is established, digoxin is administered once daily at the same time each day. 1
Standard Maintenance Intervals:
- Once daily dosing is the standard for all adult patients 1
- Divided daily dosing (twice daily) is recommended only for infants and children under age 10 1
- Typical adult maintenance doses range from 0.0625-0.25 mg once daily, based on age, renal function, and lean body weight 1
Time to Steady State:
- Steady-state serum concentrations are achieved in approximately 5 half-lives (1-3 weeks depending on renal function) when no loading dose is given 1
- With normal renal function (CrCl 60 mL/min), steady state is reached in approximately 11 days 1
Important Timing Considerations
Serum Level Sampling:
Blood samples for digoxin levels must be drawn at least 6-8 hours after the last dose to allow adequate time for equilibration between serum and tissue. 1
- On once-daily dosing, the concentration will be 10-25% lower when sampled at 24 hours versus 8 hours post-dose, depending on renal function 1
- On twice-daily dosing (pediatric), there are only minor differences whether sampling occurs at 8 or 12 hours after a dose 1
Common Pitfall to Avoid
Do not interrupt digoxin therapy with "drug holidays" (e.g., stopping 2 days per week). This outdated practice reduces plasma concentrations to subtherapeutic levels (dropping by 40-50%) and does not prevent toxicity. 5 Instead, adjust the daily dose based on creatinine clearance to maintain therapeutic levels of 0.5-0.9 ng/mL while preventing toxicity. 6, 5