Pharmacokinetics

Pharmacokinetics is the branch of pharmacology that studies the movement and fate of drugs within the body over time. It involves understanding how a drug is absorbed, distributed, metabolized, and excreted, collectively referred to as ADME. These processes determine the concentration of a drug in the systemic circulation and various tissues, influencing its therapeutic effectiveness and potential toxicity.

Absorption describes how a drug enters the bloodstream from the site of administration, which can vary depending on the route, such as oral, intravenous, or topical. Distribution involves the dispersion of the drug throughout body fluids and tissues, influenced by factors like blood flow, tissue permeability, and binding to plasma proteins.

Metabolism primarily occurs in the liver and involves chemical modifications of the drug to facilitate elimination. It often transforms lipophilic compounds into more hydrophilic forms through enzymatic processes, particularly by cytochrome P450 enzymes. Excretion is the removal of the drug and its metabolites from the body, mainly through renal filtration, but also via biliary secretion, lungs, sweat, or saliva.

Pharmacokinetics is crucial in determining dosing regimens, predicting drug interactions, and understanding variations in drug response among individuals. It is integrated with pharmacodynamics, the study of biological effects, to optimize drug therapy. Mathematical modeling, such as compartmental analysis, helps quantify pharmacokinetic parameters like half-life, volume of distribution, clearance, and area under the curve (AUC).

Understanding pharmacokinetics is essential for drug development, clinical pharmacology, and personalized medicine, ensuring drugs are used safely and effectively across diverse patient populations.