IC50

From Wikipedia, the free encyclopedia

The introduction to this article provides insufficient context for those unfamiliar with the subject matter.
Please help improve the introduction to meet Wikipedia's layout standards. You can discuss the issue on the talk page.

IC₅₀, the half maximal inhibitory concentration, represents the concentration of an inhibitor that is required for 50% inhibition of its target (i.e. an enzyme, cell, cell receptor or a microorganism. IC₅₀ values are dependent on conditions under which they are measured. For example for enzymes, IC₅₀ value increases as enzyme concentration increases. Furthermore depending on the type of inhibition other factors may influence IC₅₀ value; for ATP dependent enzymes IC₅₀ value has an interdependency with concentration of ATP, especially so if inhibition is all of it competitive.

It's commonly used as a measure of drug effectiveness. Another measure of drug efficacy is EC₅₀ which represents the concentration of a compound that is required to obtain 50% of the maximum effect in vivo. (Ex. EC₁₀₀ would be the minimum concentration of a compound to obtain 100% of its effect).

According to the FDA, IC₅₀ represents the concentration of a drug that is required for 50% inhibition in vitro whereas EC₅₀ represents the plasma concentration required for obtaining 50% of a maximum effect in vivo.(http://www.fda.gov/ohrms/dockets/ac/00/slides/3621s1d/sld036.htm)