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Renal clearance of digoxin in young infants
Insights
Infants with heart failure show increasing digoxin renal clearance with age, reaching adult levels by five months. Digoxin clearance is significantly higher than creatinine clearance in infants, explaining higher dosage needs.
Area of Science:
- Pediatric Nephrology
- Clinical Pharmacology
- Cardiology
Background:
- Infants with congenital heart disease and heart failure often require digoxin therapy.
- Understanding drug clearance in infants is crucial for appropriate dosing.
- Renal function and drug metabolism differ significantly between infants and adults.
Purpose of the Study:
- To investigate the age-dependent changes in renal clearance of digoxin and creatinine in infants.
- To compare digoxin and creatinine renal clearances in infants with heart failure.
- To elucidate the pharmacokinetic basis for digoxin dosage requirements in this population.
Main Methods:
- Measurement of renal clearance of digoxin and creatinine in eleven infants (1-5 months old) with congenital heart disease and heart failure.
- Simultaneous determination of clearances at various time points.
- Calculation of digoxin to creatinine clearance ratios.
Main Results:
- Renal clearance of digoxin was low at one month (50 ml/min/1.73 m2) and increased to adult levels by five months (130-150 ml/min/1.73 m2).
- Digoxin clearance was consistently higher than creatinine clearance in infants (mean ratio 1.73).
- This contrasts with older subjects where clearances are typically similar.
Conclusions:
- Infant renal digoxin clearance matures significantly between one and five months of age.
- The higher digoxin clearance relative to creatinine in infants contributes to their increased digoxin dosage requirements.
- These findings have implications for optimizing digoxin therapy in pediatric heart failure.
Abstract:
The renal clearance of digoxin and creatinine were measured in eleven infants, aged one to five months, with congenital heart disease and heart failure. The renal clearances of digoxin were low at one month of age (50 ml/min/1.73 m2) but increased progressively until the adult range was attained at about five months of age (130-150 ml/min/1.73 m2). At any given age, however, the renal clearance of digoxin was almost twice as great as the simultaneously determined creatinine clearance (mean ratio 1.73). This stands in marked contract to older subjects where creatinine and digoxin clearances are usually similar. These data explain (in part) the larger digoxin dosage requirement of infants.