The equations were validated against commercial software [NONMEM (Beal, Sheiner, Boeckmann, & Bauer, 2009)] output to assess their capability to handle both complex dosage regimens and the effect of changes in covariate/parameter values that may occur at discrete times within or between dosing intervals.


 For all tested pharmacokinetic models, the time-course of drug amounts using the ADVAN-style analytical solutions were identical to NONMEM outputs to at least four significant figures, confirming the validity of the presented equations.



NONMEM
The equations were coded in the R language and used to simulate the time-course of drug amounts in each compartment of the systems. 
R language
Journal of pharmacological and toxicological methods
D007262:Infusions, Intravenous; D008954:Models, Biological; D008962:Models, Theoretical; D004364:Pharmaceutical Preparations
Abuhelwa Ahmad Y AY ;Foster David J R DJ ;Upton Richard N RN 