Relationship Between Pharmacokinetics and Pharmacogenomics and Its Impact on Drug Choice and Dose Regimens (2018)

Abstract

Definition Pharmacokinetics can be defined as the relationship between the administered dose and the plasma concentration of a drug, which implies the study of the different processes of absorption, distribution, metabolism, and excretion, in short “what the organism does with the drug”. Pharmacokinetics determines the concentration of drugs in the drug-exposed subject and therefore contributes to the intensity of the observed response. Modifications in pharmacokinetics help explaining different responses among different individuals, where different physiological situations may be found, including short or advanced age, organic failure (renal, hepatic), hypo-hypervolemia, etc. Pharmacokinetic parameters vary among subjects and also depending on the route of administration. As shown in Fig. 8.1 (right superior box), the first part of the curve represents the absorption process. The kinetics of absorption depends on the interplay between passive and active absorption and the activity of efflux pumps. When the drug is absorbed, it could go to the systemic circulation without modifications or suffer a first-step metabolism. Absorption-related processes and first-pass metabolism could affect the maximum level that the drug can achieve (plasmatic peak). The second part of the curve is dominated by the elimination or excretion process. Here the metabolism of the drug and its urinary and fecal excretion are the most important processes.