Which term studies the rate at which drug concentrations change in the body?

• A. Pharmacodynamics
• B. Absorption
• C. Pharmacokinetics
• D. Elimination

Answer: (C)

The rate at which drug concentrations change in the body is described by pharmacokinetics. It covers how the body handles a drug from administration through absorption into the bloodstream, distribution to tissues, metabolism, and eventual elimination. This time course governs how quickly concentrations rise after dosing and how quickly they fall as the drug is cleared, with parameters like half-life, clearance, and volume of distribution shaping those rates. Pharmacodynamics, by contrast, focuses on the drug’s effects on the body, not the concentration changes. Absorption is only one step in the process, and elimination is the final phase; the study that explains the overall rate of concentration change is pharmacokinetics.