farmakokinetiske

Farmakokinetiske, commonly called pharmacokinetics, is the study of how the body handles a drug after administration. It describes the time course of drug concentrations in blood and tissues and the processes of absorption, distribution, metabolism, and excretion (ADME). It distinguishes what the body does to the drug from what the drug does to the body (pharmacodynamics).

Absorption concerns how a drug enters the bloodstream, affected by route, formulation, and physiology. Distribution covers the dispersion through body fluids and into tissues, influenced by perfusion and protein binding. Metabolism mainly occurs in the liver, producing more water-soluble metabolites via phase I and II reactions, while some drugs are activated as prodrugs. Excretion removes drugs and metabolites, primarily through the kidneys and bile.

Important pharmacokinetic parameters include bioavailability (F), clearance (CL), and the volume of distribution (Vd). The half-life (t1/2) describes how long until concentrations fall by half. Cmax and Tmax characterize absorption, and the area under the concentration–time curve (AUC) reflects overall exposure.

Variability in pharmacokinetics arises from age, weight, organ function, genetics, disease, and drug interactions. Pharmacokinetic modeling, such as population PK and physiologically based PK, informs dosing regimens and therapeutic drug monitoring. This knowledge supports dose adjustments in renal or hepatic impairment and in special groups like children, elderly, or pregnant patients.