OECD 425: Acute Oral Toxicity – Up-and-Down Procedure

The OECD 425 Acute Oral Toxicity procedure, also known as the “Up-and-Down Procedure”, is used for determining the acute toxicity of a chemical when taken orally. At a high level, the test involves a stepwise oral dosing procedure and observation of a small number of laboratory animals to determine the toxicity of a substance. The study design follows the current OECD Test Guideline entitled “Test No. 425: Acute Oral Toxicity: Up-and-Down Procedure” and is performed on rodents (typically rats) and in accordance with Good Laboratory Practice regulations. This test is part of the Acute Toxicity Six-Pack tests.

How the OECD 425 Acute Oral Toxicity – Up-and-Down Procedure is Performed

This test guidance is comprised of both a limit test and a main test procedure.

OECD 425 Limit Test

The Limit Test is conducted in scenarios where there is information indicating that the test material is non-toxic. It is a sequential test that uses a maximum number of 5 test subjects. A test dose of 2000 mg/kg or when required by specific regulatory needs, 5000 mg/kg may be used. All test subjects will be observed for 14-days following administration.

OECD 425 Main Test

In situations where there is limited information about toxicity or if a limit test has been performed and the substance has moderate toxicity, the main test should be performed. The Main Test procedure involves dosing test subjects one at a time and observing them for a minimum of 48 hours before deciding on the next dose level.

Typically 20 grams of test article are required. This test is performed in compliance with Good Laboratory Practice Regulations.

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