EC50

For the UK postcode EC50, see EC postcode area.

The term half maximal effective concentration (EC₅₀) 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 EC₅₀ 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 IC₅₀ which is a measure of a compound's inhibition (50% inhibition). For competition binding assays and functional antagonist assays IC₅₀ is the most common summary measure of the dose-response curve. For agonist/stimulator assays the most common summary measure is the EC₅₀.

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 IC₅₀. This can be determined mathematically by derivation of the...
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