LAUSR

On account of the disturbance from the distribution phase, the concentration-time curve of drugs cannot fully reflect the characteristics of elimination, and thus, it is difficult for present methods to obtain ideal pharmacokinetic parameters. This paper presents a method to determine pharmacokinetic parameters based on an andante constant-rate intravenous infusion. A mathematical model of the constant-rate intravenous infusion combined with the elimination of first-order kinetics was established. During infusion, the accumulation tendency of drugs was deduced as $${C}_{t}={C}_{{0}}+({C}_{ss}-{C}_{{0}})\cdot (1-{e}^{-Kt})$$Ct=C0+(Css−C0)⋅(1−e−Kt) using the principle of calculus. Then, the method to determine the pharmacokinetic parameters was summed up. After collecting the blood drug concentration (Ct) -time (t) data from a constant-rate (v) infusion period, an exponential regression analysis was conducted to obtain the elimination rate constant (K) and plateau concentration (Css). Then, the half-life (t1/2), apparent volume of distribution (Vd) and clearance rate (CL) were calculated based on the equations, t1/2 = 0.693/K, Vd = (v/K)/Css and CL = v/Css, respectively. In addition, an application example of cimetidine in a beagle dog was used to demonstrate the implementation process of the method.