Test No. 425: Acute Oral Toxicity: Up-and-Down Procedure

         The method permits estimation of an LD50 with a confidence interval and the results allow a substance to be classified for acute toxicity according to the Globally Harmonised System of classification and labelling of chemicals.         It is easiest to apply to materials that produce death within couple of days. This Test Guideline is intended for use with rodents (rat female preferably). There are a limit test and a main test. The limit test can be used efficiently to identify chemicals that are likely to have low toxicity. The test substance is administered generally in a single dose by gavage to animals fasted prior to dosing. Single animals are dosed in sequence usually at 48h intervals. The first animal is dosed a step below the best preliminary estimates of the LD50. The second animal receives a lower dose (if the first animal dies) or a higher dose (if the first animal survives). Animals are observed with a special attention given during the first 4 hours and daily thereafter, for a total of 14 days generally. Weights Animals should be determined at least weekly. All the animals should be subjected to gross necropsy. Globally the LD50 is calculated using the maximum likelihood method. Following this, it may be possible to compute interval estimates for the LD50 most narrow is the interval and better is LD50 estimation.         Software to be used with TG 425, 432, 455. Click here. Software not part of the Mutual Acceptance of Data.      