Pharmacokinetic Models and Equations Pharmacokinetic models are useful to describe data sets, to predict serum concentrations after several doses or different routes of administration, and to calculate pharmacokinetic constants such as CL, V D , and t 1/2 . 11 Compartmental models depict the body as one or more discrete compartments to which a drug is distributed and/or from which a drug is eliminated. The shape of the serum-concentration-versus-time curve determines the number of compartments in the pharmacokinetic model and the equation used in computations . First-order rate constants, known as microconstants , describe the rate of transfer from one compartment to another. Each compartment also has its own V D . For clinical dosage adjustment purposes using drug concentrations, a one-compartment model is the most commonly used pharmacokinetic model. Visual representations of one- and two-compartment drug-distribution models One-Compart...