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Acute Oral Toxicity: Up- and- down Procedure 

As per TG 425 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 Harmonized System of the classification and rebelling of chemicals. It is easiest to apply to materials that product death within couple of days. This test guideline is intended for use with rodents, used preferably rat female. There are 2 test one is limit test and a main test. The limit test can be used efficiently to identify chemicals are likely know the low toxicity. The single dose of test stance is administered by gavage to animals fasted prior to dosing. Single animal are dosed in sequence using at 48 h intervals. The first animal is dosed a step below the best preminary estimates of the LD 50. The 2nd animal receives a lower dose in case 1st animal was dies or higher dose in case of 1st animal is survives. The animals are observed with special attention given during the 1st 4 hours and daily thereafter, for a total of 14 days generally. The weights of animals should be determined at least weekly. All the animals should be subject to gross necropsy. Globally the LD50 is calculated using the maximum likelihood method. Making follow up above it may be possible to compute interval estimates for the LD50, most narrow is interval and better is LD50 can be determine.