PHARMACOKINETICS: BASIC CONSIDERATIONS

Pharmacokinetics is the branch of pharmacology that quantitatively studies the time course of drug absorption, distribution, metabolism, and excretion (ADME) within the body. These processes determine the concentration of a drug at its site of action and thereby influence its therapeutic efficacy and safety. Understanding pharmacokinetics is essential for designing optimal dosage regimens, predicting drug interactions, and tailoring treatments to individual patient needs.

Key pharmacokinetic parameters include:

• Absorption: The process by which a drug enters systemic circulation from its site of administration. Influenced by solubility, permeability, and route of administration.
• Distribution: The dispersion of drug molecules throughout body fluids and tissues. Governed by factors such as plasma protein binding and tissue affinity.
• Metabolism: Biotransformation of drugs, primarily in the liver, into active or inactive metabolites. Enzyme systems like cytochrome P450 play a central role.
• Excretion: Removal of drugs from the body, mainly via renal or biliary pathways.

Quantitative descriptors such as:

• Cmax (peak plasma concentration)
• Tmax (time to reach Cmax)
• AUC (area under the plasma concentration-time curve)
• Half-life (t½) and
• Clearance (CL)

are used to evaluate drug exposure and guide dosing strategies. Pharmacokinetic models—compartmental and non-compartmental—help simulate drug behavior and predict outcomes under various clinical scenarios.

A thorough grasp of pharmacokinetic principles enables clinicians and researchers to ensure safe, effective, and personalized drug therapy.