Digoxin pharmacokinetics: multicompartmental analysis and its clinical implications.

The kinetics of digoxin have been investigated in healthy volunteers using an isotopic tracer technique. A three compartment open kinetic model has been proposed as the simplest model consistent with the plasma, urinary and faecal data obtained. The renal clearance of digoxin (mean +/- s.d.) was found to be 119+/-10 ml/min, which did not differ significantly from the glomerular filtration rate (110+/-14 ml/min). Digoxin extra-renal clearance (mean+/-s.d.) was found to be 47+/-7 ml/min. The model predicts that the tissue concentration attained after four 0.25 mg oral doses spread over 24 h can be achieved within a period of 4 h following a single oral loading dose of 1 mg. Maintenance doses can be derived from a simple formula based on the glomerular filtration rate, extra-renal clearance and bioavailability of the digoxin preparation used.