In toxicology, the median lethal dose, LD50 (abbreviation for “lethal dose, 50%”), LC50 (lethal concentration, 50%) or LCt50 (lethal concentration & time) of a toxin, radiation, or pathogen is the dose required to kill half the members of a tested population after a specified test duration. LD50 figures are frequently used as a general indicator of a substance's acute toxicity. The test was created by J.W. Trevan in 1927. The term semilethal dose is occasionally used with the same meaning, in particular in translations from non-English-language texts, but can also refer to a sublethal dose; because of this ambiguity, it is usually avoided. LD50 is usually determined by tests on animals such as laboratory mice. In 2011 the U.S. Food and Drug Administration approved alternative methods to LD50 for testing the cosmetic drug BOTOX.
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