Potency of a drug. Equipotent drug definition

The following pharmacology definition has been taken from the Pharmacology and Experimental Therapeutics Department Glossary at Boston University School of Medicine.


Equally potent, or equally capable of producing a pharmacologic effect of a specified intensity. The masses of the drugs required to produce this degree of effect may be compared, quantitatively, to yield estimates of ” potency” of the drugs. Obviously, if two drugs are not both capable of producing an effect of a given intensity, they cannot be compared with respect to potency; i.e., drugs with different intrinsic activities or ceiling effects cannot be compared with respect to potency in doses close to those producing the ceiling effect of the drug with the greater intrinsic activity.

The copyright of the text is hold by Trustees of Boston University. Permission has been granted for its use in this blog.

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