Plasma terminal half‐life

Terminal plasma half‐life is the time required to divide the plasma concentration by two after reaching pseudo‐equilibrium, and not the time required to eliminate half the administered dose. When the process of absorption is not a limiting factor, half‐life is a hybrid parameter controlled by plasma clearance and extent of distribution. In contrast, when the process of absorption is a limiting factor, the terminal half‐life reflects rate and extent of absorption and not the elimination process (flip‐flop pharmacokinetics). The terminal half‐life is especially relevant to multiple dosing regimens, because it controls the degree of drug accumulation, concentration fluctuations and the time taken to reach equilibrium.