“EC50”的意思、由来-开放百科全书

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EC50

释义

Equation
Limitations
See also
References
External links

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 a specified exposure time.^[1] It is commonly used as a measure of a drug's potency. EC₅₀ is expressed in molar units (M), where 1 M is equivalent to 1 mol/L.

The EC₅₀ of a graded dose response curve therefore represents the concentration of a compound where 50% of its maximal effect is observed.^[2]

The EC₅₀ of a quantal dose response curve represents the concentration of a compound where 50% of the population exhibit a response,^[3] 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.^[4] The half maximal effective concentration is sometimes also expressed as pEC₅₀ instead of EC₅₀, where:

A small change in ligand concentration typically results in rapid changes in response in the biological system, following a sigmoidal function. The inflection point at which the increase in response with increasing ligand concentration begins to slow is the EC₅₀, which can be mathematically determined by derivation of the best-fit line. While relying on a graph for estimation is more convenient, this typical method yields less accurate results and less precise.^[5]

Equation

Many different equations can be used to derive an EC₅₀. One possible function is:

where Y is the observed value, Bottom is the lowest observed value, Top is the highest observed value, and the Hill coefficient gives the largest absolute value of the slope of the curve.^[6]

Limitations

The effects of a stressor or drug generally depend on the exposure time. Therefore, the EC₅₀ (and similar statistics) will be a function of exposure time. The exact shape of this time function will depend upon the stressor (e.g., the specific toxicant), its mechanism of action, the organism exposed, etc. This time dependency hampers the comparison of potency or toxicity between compounds and between different organisms.

References

1. ^Introducing dose response curves {{webarchive|url=https://web.archive.org/web/20070219185355/http://www.graphpad.com/curvefit/introduction89.htm |date=2007-02-19 }}, Graphpad Software
2. ^EC50 definition
3. ^definition of EC₅₀ for quantal dose response curve
4. ^Assay Operations for SAR Support {{webarchive|url=https://web.archive.org/web/20061129102848/http://www.ncgc.nih.gov/guidance/section3.html |date=2006-11-29 }} NIH Chemical Genomics Center
5. ^Assay Operations for SAR Support {{webarchive|url=https://web.archive.org/web/20061129102848/http://www.ncgc.nih.gov/guidance/section3.html |date=2006-11-29 }} NIH Chemical Genomics Center
6. ^EC50 equation {{webarchive|url=https://web.archive.org/web/20120417121807/http://www.sigmaplot.com/products/sigmaplot/Standard_Curves_Analysis.pdf |date=2012-04-17 }} - see page 5

External links

[https://web.archive.org/web/20060517233647/http://www.unmc.edu/Pharmacology/receptortutorial/competition/IC50.htm Determination of IC₅₀ values]
Neubig et al. International Union of Pharmacology Committee on Receptor Nomenclature and Drug Classification. XXXVIII. Update on terms and symbols in quantitative pharmacology. Pharmacol Rev. 2003 Dec;55(4):597-606.

2 : Pharmacodynamics|Toxicology

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Equation

Limitations

See also

References

External links