IC50

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    Graphical representation of the IC50 determination of the inhibition of an enzyme's activity by a small molecule ("drug"). Four different concentrations of the small molecule (ranging from 30 to 300 μM) were tested.

    Half maximal inhibitory concentration (IC50) is a measure of the potency of a substance in inhibiting a specific biological or biochemical function. IC50 is a quantitative measure that indicates how much of a particular inhibitory substance (e.g. drug) is needed to inhibit, in vitro, a given biological process or biological component by 50%. The biological component could be an enzyme, cell, cell receptor or microorganism. IC50 values are typically expressed as molar concentration.

    IC50 is commonly used as a measure of antagonist drug potency in pharmacological research. IC50 is comparable to other measures of potency, such as EC50 for excitatory drugs. EC50 represents the dose or plasma concentration required for obtaining 50% of a maximum effect in vivo.

    IC50 can be determined with functional assays or with competition binding assays.

    Sometimes, IC50 values are converted to the pIC50 scale.

    Due to the minus sign, higher values of pIC50 indicate exponentially more potent inhibitors. pIC50 is usually given in terms of molar concentration (mol/L, or M), thus requiring IC50 in units of M.[1]

    See Also[edit | edit source]

    References[edit | edit source]

    1. Stewart MJ & Watson ID: Standard units for expressing drug concentrations in biological fluids. Br J Clin Pharmacol 1983. (PMID 6882621) [PubMed] [DOI] [Full text]