Pharmacometrics

The term pharmacometrics may have been first proposed by Benet and Rowland (1982), the editors of the Journal of Pharmacokinetics and Biopharmaceutics (which later became the Journal of Pharmacokinetics and Pharmacodynamics), announcing a new journal section called Pharmacometrics. They defined pharmacometrics as “the design, modeling and analysis of experiments involving complex dynamic systems in the field of pharmacokinetics and biopharmaceutics.” As the journal evolved into one that primarily focused on pharmacometrics methods and applications, biopharmaceutics—the study of the role of pharmaceutical formulations in the pharmacokinetics of drugs, was subsumed under pharmacokinetics and replaced with pharmacodynamics. Thus, a more up-to-date definition of pharmacometrics is the design and modeling of data involving complex dynamic systems in the fields of pharmacokinetics (PK) and pharmacodynamics (PD). At the core of pharmacometrics is the development of more specific statistical models with structure based on the scientific disciplines of PK and PD to describe the time-course of drug exposure (PK) and the exposure–response relationship (PK/PD). In simplest terms, Katzung et al. (2004) defines pharmacokinetics as the study of what “the body does to the drug” and pharmacodynamics as the study of what “the drug does to the body.” Pharmacokinetics is composed of the following processes: absorption, distribution, metabolism, and elimination of drugs administered to a body, the collective commonly referred to as ADME. In pharmacometrics, systems of differential equations are used to characterize these PK processes in a body.