Dose-response

Dose-response describes the relationship between the amount of a substance given and the size or likelihood of the effect it produces.

Researchers map this relationship by testing several doses and plotting the results, which typically produces a curve that rises and then flattens as receptors become saturated. The shape reveals the threshold below which nothing measurable happens, the range where effect increases with dose, and the plateau. Some compounds show unusual shapes, such as a bell or inverted U, in which a middle dose produces more effect than higher or lower doses. Establishing dose-response is a core step in drug development and in toxicology.

Cannabidiol has shown nonlinear dose-response patterns in some preclinical and small human studies, which is one reason findings at one dose cannot be scaled to another. Retail products span a wide range of concentrations, and few have been tested in controlled dose-ranging studies. Readers meet the concept in research summaries and in discussions of why results vary. It describes how a population responded in a study and does not identify an optimal amount for anyone in particular.