What do pharmacology, pharmacokinetics, and pharmacodynamics mean?

Pharmacology is the broad study of how substances interact with biological systems. Two of its central subfields are frequently confused: pharmacokinetics is the study of what a biological system does to a compound — absorption, distribution, metabolism, and elimination. Pharmacodynamics is the study of what the compound does to the biological system — its effects and mechanism of action.

A compound’s biological half-life is the time it takes for half of an administered amount to be cleared from the body — a pharmacokinetic property. Bioavailability describes the proportion of an administered amount that reaches systemic circulation in an active form. A biomarker is a measurable indicator of a biological state or process; a metabolite is a substance produced when the body breaks a compound down.