IC50

'IC₅₀' is a measure of concentration used in pharmacological research. IC₅₀, or 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). In simpler terms, it measures how much of a particular substance/molecule is needed to inhibit some biological process by 50%.
IC₅₀ is commonly used as a measure of drug affinity. A measure of drug efficacy is Half maximal effective concentration (EC₅₀) which represents the concentration of a compound that is required to obtain 50% of the maximum effect ''in vivo''. (Ex. EC₉₉ would be the minimum concentration of a compound to obtain 99% of its effect). 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.^[1]
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''.^[2]
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.

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See also

References

External links

See also

★ Dose-response relationship

★ CC₅₀

★ LD₅₀

References

1. http://www.ncgc.nih.gov/guidance/section3.html
2. http://www.fda.gov/ohrms/dockets/ac/00/slides/3621s1d/sld036.htm

External links

★ Online IC50 Calculator