Quantal Responses Calculation of ED50 Screening Methods in Pharmacolgy, Academic Press, New York, 61-63

Author(s): Turner RA,


The most common test of acute toxicity is the LD50 test. LD50 means, if administered dose of drug to animal group, for experimental purpose for the estimation of therapeutic effectiveness kills 50% of animals, than it means that particular dose of drug is lethal dose 50 (LD50). It was developed in 1920’s and called “classical LD50” involved 100 animals for 5 dose-groups, later in 1981 it was modified by the Organization for Economic Co-operation and Development (OECD) and reduced number upto 30 for 3 dose-groups. Methods to calculate LD50 values are - Litchfield and Wilcoxson, Reed-Muench, Miller-Tainter and Karber’s method. But all these methods require large number of animals. Factors which affect the results of LD50 are- Species, Age, Sex, Amount of food, Social environment etc. LD50 study has some Limitations and results may vary greatly. Due to excess of animal sacrifice we should go to alternative methods which minimum number of animals is required. FRAME (Fund for the Replacement of Animals in Medical Experiment) believes that the lethal dose test is unnecessarily cruel and scientifically invalid. Several countries, including the UK, have taken steps to ban the oral LD50. The OECD, the international governments’ advisory body abolished the requirement for the oral test in 2001. Three alternative methods and these are: Fixed Dose Procedure (FDP)-OECD TG 420, Acute Toxic Class method (ATC)-OECD TG 423, Up-and-Down Procedure (UDP)-OECD TG 425. These methods only consider signs of toxicity in place of death. Signs recorded during studies like; increased motor activity, anaesthesia, tremors, arching and rolling. Alternative methods save numbers experimental animals. _____________________________________

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