A Population Pharmacokinetic Approach to Describe Cephalexin Disposition in Adult and Aged Dogs

Table 2

Pharmacokinetic model building.

Model	Change in objective function	Percentage of the interindividual variability of the pharmacokinetic parameter (%)
Univariate analysis
Effect of age on Tlag; Tlag = Tlagtypical	−5	25.2
Effect of age on Vd/F; Vd/F = Vd/Ftypical	−5	20.7
Effect of age on ke/F; Ke/F = Ketypical	−6	23.8
Effect of breed on Vd/F; Vd/F = Vd/F	−9	38.3
Effect of sex on ke/F; Ke/F = Ketypical	−5	19

Tlag: lag-time; ke/F, apparent elimination rate constant; Vd/F, apparent volume of distribution.
References: effect of age: 0 = adult; 1 = aged dog; effect of breed: 0 = mixed breed, 1 = Beagle; effect of sex: 0 = female, 1 = male. For all models, the residual variability was modelled as a combination error model.