The following pharmacology definition has been taken from the Pharmacology and Experimental Therapeutics Department Glossary at Boston University School of Medicine.
EC50
The concentration of an agonist that produces 50% of the maximal possible effect of that agonist. Other percentage values (EC10, EC20, etc.) may be specified. Concentration is preferably expressed in molar units, but the mass concentration (g/l) may be used if the molecular weight of the substance is unknown.
The copyright of the text is hold by Trustees of Boston University. Permission has been granted for its use in this blog.