Ic50

IC50

The half maximal inhibitory concentration (IC₅₀) is a measure of the effectiveness of a compound in inhibiting biological or biochemical function. This quantitative measure indicates how much of a particular drug or other substance (inhibitor) is needed to inhibit a given biological process (or component of a process, i.e. an enzyme, cell, cell receptor or microorganism) by half. In other words, it is the half maximal (50%) inhibitory concentration (IC) of a substance (50% IC, or IC₅₀). It is commonly used as a measure of antagonist drug potency in pharmacological research. Sometimes, it is also converted to the pIC₅₀ scale (pIC₅₀ = -log IC₅₀), in which higher values indicate exponentially greater potency. According to the FDA, IC₅₀ represents the concentration of a drug that is required for 50% inhibition in vitro. It is comparable to an EC₅₀ for agonist drugs. EC₅₀ also represents the plasma concentration required for obtaining 50% of a maximum effect in vivo.