CC5 – Dose/concentration-response relationship

CC5. Dose/concentration–response relationship is the relationship between the dose/concentration of a drug and the magnitude of the response produced.

5.1. Dose/concentration–response relationship can be graphically depicted as a curve with the dose/concentration on the x-axis and the response on the y-axis.

5.2. For ease of visualisation, the x-axis of the dose/concentration–response is converted to a logarithmic scale that results in a sigmoid (s) shape known as the log dose/concentration–response curve.

5.3. Dose refers to the amount of drug administered in vivo to an organism (e.g., mg or mg kg^-1) while concentration refers to in vitro/ex vivo the amount of drug per unit volume (e.g., ng ml^-1 or μM).

5.4. From a graded dose/concentration–response curve, the potency (measured as the ED₅₀ or EC₅₀ for an agonist, or IC₅₀, Kb or pA2 for an antagonist) and the maximal response (E_max) of a drug can be determined.

5.5. Dose/concentration–response curves enable the pharmacodynamic responses of drugs to be compared and contrasted, and to determine whether drugs are full agonists, partial agonists, inverse agonists or antagonists.

5.6. A quantal dose–response curve reflects the frequency of a defined response in a population at different doses of the drug rather than the fraction of maximal response, as reflected on a graded response curve.