8 Drug Efficacy And Potency

Efficacy is the ability of a drug after binding with receptors to initiate change which leads to certain effects. Simply, Efficacy (Emax) is the capacity of a drug to produce a maximum response. Also, it is known as maximal efficacy. In other words, Efficacy is the maximal response that can be elicited by the drug. In other words, Efficacy is the ability of a drug to elicit a physiologic response when it interacts with a receptor.

On the other hand, Potency is a comparative measure of different doses of two drugs that are needed to produce the same pharmacological effect. It is also known as drug strength. Simply, Potency is the amount of drug needed to produce a certain response.

In other words, Potency refers to the concentration (EC50) or dose (ED50) of a drug required to produce 50% of that drug’s maximal effect. Certainly, more the ED 50 of a drug, less the potency and Less the ED50, more the potency. Potency is a measure of the amount of drug necessary to produce an effect of a given magnitude .