Median Lethal Dose

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.