Which phase relates dose to plasma concentration over time?

• A. Pharmaceutic
• B. Pharmacodynamic
• C. Pharmacogenomic
• D. Pharmacokinetic

Answer: (D)

Pharmacokinetics is the discipline that relates dose to plasma concentration over time. It explains how the body absorbs the drug, distributes it, metabolizes it, and eliminates it, forming the concentration-time curve after a dose. This curve shows how much drug is in the plasma at any moment and how long exposure lasts, which is essential for dosing decisions. Pharmacodynamics studies what the drug does to the body, including receptor binding and effect magnitude. Pharmacogenomics looks at how genetic differences affect drug response. Pharmaceutics concerns the formulation and dissolution of the drug product, influencing absorption but not the full dose-to-concentration time relationship by itself.