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In pharmacology, potency or biological potency [1] is a measure of a drug's biological activity expressed in terms of the dose required to produce a pharmacological effect of given intensity. [2]
The term "potency" refers to the EC 50 value. The lower the EC 50 , the less the concentration of a drug is required to produce 50% of maximum effect and the higher the potency. The EC 10 and EC 90 concentrations to induce 10% and 90% maximal responses are defined similarly.
Intrinsic activity (IA) and efficacy (E max) refer to the relative ability of a drug-receptor complex to produce a maximum functional response. This must be distinguished from the affinity, which is a measure of the ability of the drug to bind to its molecular target, and the EC 50, which is a measure of the potency of the drug and which is proportional to both efficacy and affinity.
Efficacy is the ability to perform a task to a satisfactory or expected degree. The word comes from the same roots as effectiveness , and it has often been used synonymously, although in pharmacology a distinction is now often made between efficacy and effectiveness .
In pharmacology, an effective dose (ED) or effective concentration (EC) is the dose or concentration of a drug that produces a biological response. [1] [2] The term "effective dose" is used when measurements are taken in vivo, while "effective concentration" is used when the measurements are taken in vitro.
The parameters of the dose response curve reflect measures of potency (such as EC50, IC50, ED50, etc.) and measures of efficacy (such as tissue, cell or population response). A commonly used dose–response curve is the EC 50 curve, the half maximal effective concentration, where the EC 50 point is defined as the inflection point of the curve.
The graph shown represents the conc-response for two hypothetical receptor agonists, plotted in a semi-log fashion. The curve toward the left represents a higher potency (potency arrow does not indicate direction of increase) since lower concentrations are needed for a given response. The effect increases as a function of concentration.
Potency is a measure of how much a drug is required in order to produce a particular effect. Therefore, only a small dosage of a high potency drug is required to induce a large response. The other terms used to measure the ability of a drug to trigger a response are: Intrinsic Activity which defines: Agonists as having Intrinsic Activity = 1