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Searching for Replacement of the LD50 Test

Project title:  

Searching for Replacement of the LD50 Test  

Project leader:  

Gerhard Zbinden  

Financial support:    
Project background:

The aim of the study was to critically follow up multiple studies that had used the classical “Lethal Dose 50 (LD50)” procedure to recognize the lethal dose of a substance in the field of toxicology.  

The determination of the LD50 was originally introduced as a simple test to obtain general information on the potency or the potential acute hazard of a chemical substance. To find the lethal dose, typically rats or mice (but also rabbits, dogs or monkeys) are divided into 4 to 5 experimental groups of a minimum of 5 (but usually 8-10 or more) animals per dose group. Each group receives a certain dose of the tested compound. The substance is given via oral or dermal application, inhalation or via injection. The different dose levels are selected in such a way that 0% up to 100% of the animals will die. Observation time lasts from 1 to 4 weeks. The particular dose with which 50% of the animals die is then referred to as the LD50 dose. This test has been widely used since its development in 1927 and is still being used as a standard test by researchers, as well as for testing toxicity of some cosmetics and lifestyle products.  

Since the early 1980s, more and more criticisms were made about the LD50 test, saying that it was highly unethical to cause a high number of animals severe suffering due to the large side effects leading to the death of the animals. Zbinden and Flury-Roversi published their review article in 1981, questioning the validity of the model due to the large number of variable factors.   According to Google Scholar, the Zbinden & Flury-Roversi’s review article financed by the Animalfree Research has been cited over 200 times in other scientific papers.    




Zbinden G., Flury-Roversi M. (1981): Significance of LD50-Test for the Toxicological Evaluation of Chemical Substances. Archives of Toxicology 47: 77-99.  


Even though the classic in vivo LD50 test is still being widely performed in medical research, nowadays it is forbidden to conduct this test for the evaluation of cosmetics and other lifestyle products throughout the European Union. Since 2009 it is also forbidden to sell cosmetics which were tested in animal experiments in the EU. In medical research, the number of animals used for LD50-testing is steadily decreasing. Since 2005 three in vitro alternative methods for replacing the in vivo LD50 test received approval.