Pharmacokinetics of a single, orally administered dose of digoxin in horses

Digoxin (elixir, 0.022 mg/kg) was administered via stomach tube to healthy horses of mixed breeding and sexes. Serum digoxin concentrations reached a peak (2.21 +/- 0.6 ng/ml) at approximately 1 hour after dosing and had a half-life of 28.8 +/- 10.7 hours. Digoxin kinetics followed a triexponential curve, indicating that at least a 2 compartmental model is required to characterize the serum concentration-time curve after this route of administration. It was calculated that to achieve average serum concentrations of 1.1 ng/ml, an oral dose of 17.4 microgram of digoxin elixir/kg/day and an IV dose of 6.1 microgram of parenteral preparation/kg/day would be required. There was no significant (P greater than 0.05) alteration in base-line serum calcium, potassium, and sodium concentrations and heart rate, P-R interval, and mean arterial blood pressure.