Yes, digoxin is primarily renally excreted.
Digoxin is eliminated predominantly through the kidneys, with 50-70% of an administered dose excreted unchanged in the urine 1. Renal excretion of digoxin is proportional to glomerular filtration rate and is largely independent of urine flow 1.
Elimination Pathways
Primary route (Renal):
- 50-70% excreted unchanged in urine via passive glomerular filtration and active tubular secretion 1, 2
- Renal clearance represents approximately 70% of total clearance 3
- Digoxin clearance directly correlates with creatinine clearance 1
Secondary route (Non-renal):
- Only 16% undergoes hepatic metabolism 1
- Metabolites include 3β-digoxigenin, 3-keto-digoxigenin, and their conjugates 1
- Metabolism is NOT dependent on cytochrome P-450 system 1
- Some biliary excretion occurs via P-glycoprotein (MDR1) transport 4
Critical Clinical Implications
Dose adjustment is mandatory in renal impairment because:
- Half-life extends from 1.5-2.0 days (normal renal function) to 3.5-5 days in anuric patients 1
- Impaired renal function elevates serum digoxin levels, increasing toxicity risk 5
- Low doses (0.125 mg daily or every other day) should be used initially if patient has impaired renal function 5
Common pitfall: Digoxin is NOT effectively removed by dialysis, exchange transfusion, or cardiopulmonary bypass because most drug is tissue-bound rather than circulating in blood 1. This means that dialysis patients remain at high risk for accumulation and toxicity.
Drug interactions affecting renal clearance: Multiple medications (clarithromycin, dronedarone, erythromycin, amiodarone, itraconazole, cyclosporine, propafenone, verapamil, quinidine) can increase serum digoxin concentrations by interfering with renal P-glycoprotein transporters 5. The dose of digoxin should be reduced when these drugs are initiated.
Monitoring strategy: Because digoxin clearance is primarily renal, patients should have serum electrolytes and renal function (serum creatinine) assessed periodically 1. Target serum digoxin concentrations of 0.5-0.9 ng/mL are recommended, as levels >1.0 ng/mL are associated with increased mortality 5.