The term half maximal effective concentration (EC<sub>50</sub>) refers to the concentration of a drug, antibody or toxicant which induces a response halfway between the baseline and maximum after some specified exposure time. It is commonly used as a measure of drug's potency.
The EC<sub>50</sub> of a graded dose response curve therefore represents the concentration of a compound where 50% of its maximal effect is observed, after a specified exposure duration.
It is also related to IC<sub>50</sub> which is a measure of a compound's inhibition (50% inhibition). For competition binding assays and functional antagonist assays IC<sub>50</sub> is the most common summary measure of the dose-response curve. For agonist/stimulator assays the most common summary measure is the EC<sub>50</sub>.
Concentration measures typically follow a Sigmoid curve, increasing rapidly over a relatively small change in concentration. The point at which the effectiveness slows with increasing concentration is the IC<sub>50</sub>. This can be determined mathematically by derivation of the... Read More