Читать книгу Physiologically Based Pharmacokinetic (PBPK) Modeling and Simulations - Sheila Annie Peters - Страница 19

Drug elimination from the body may follow zero or first‐order kinetics (Figure 1.1). In zero‐order kinetics, a constant amount of the drug is eliminated in a certain time (e.g., 20 mg per hour). In first‐order processes, a constant proportion of the drug is eliminated in a certain time (e.g., 20% per hour). Though relatively rare, zero‐order kinetics may be encountered in intravenous infusions as well as in elimination of some drugs (e.g. ethanol) but will not be further elaborated here.

The temporal changes in the drug concentrations following an IV bolus injection of 50 mg of a drug with first‐order kinetics are depicted in Figure 1.2. The slope and area under the curve (AUC) are the two parameters that can be extracted from the concentration‐time profile as shown in the semilogarithmic and linear plots respectively. Other useful pharmacokinetic parameters may be derived from these two parameters, as will become evident from the mathematical derivations below.