Pharmacodynamics (PD)

Pharmacodynamics is the study of what a substance does to the body: the receptors and pathways it acts on and the relationship between concentration and effect.

If pharmacokinetics describes what the body does to a drug, pharmacodynamics describes the reverse. It covers the molecular targets a compound binds, whether it activates or blocks them, how strongly, and what physiological changes follow. Dose-response curves, receptor binding studies, and biomarker measurements are its typical tools. Pharmacodynamic interactions occur when two substances act on the same system, so their effects add or oppose each other.

Cannabidiol has a complex pharmacodynamic profile: it interacts weakly with the classical cannabinoid receptors and more notably with a range of other targets, including serotonin and TRP receptors and several enzymes, as shown mainly in laboratory studies. Which of these actions matter at the concentrations reached in people is still being investigated. Readers meet the term in research summaries explaining mechanism. Much of the pharmacodynamic evidence for CBD is preclinical and does not by itself establish clinical effects.