Pharmacokinetics of digoxin in the cat and comparisons with man and the dog

Digoxin doses of 14.3, 5.72 or 1.43 mcg/kg were administered to 8 cats and the plasma digoxin concentrations (concns) were measured as a function of time for 96 hr. Pharmacokinetic linearity was evidenced by: (1) mean plasma clearance (Clp) of 4.05 ml/(kg x min) with a coefficient of variation of 34.6% and a range of 2.69-6.71; (2) linear relationship between total area under the plasma concn-time curve and the administered dose. Further evidence for linearity was the lack of dose-dependence of apparent elimination half-life (beta). The volume of distribution and beta for cats were respectively (mean +/- s.d.) 20.4 +/- 5.35 L/kg and 0.0120 +/- 0.0030 hr-1. Results from cats were compared with literature data for dogs and man. The order of Clp in units of ml/(kg x min) were: infant greater than dog greater than cat greater than adult man.