Acute Oral Toxicity: Up and Down Procedure

This test allows substance to be classified according to the Globally Harmonised System for the classification of chemicals by using few animals compared to the traditional LD50. This procedure is practical for samples that produced death within 48 hours.

As the name suggest “ Up and Down”, this procedure is based on the premise of increasing the test  dose if the animal survived and decreasing the dose if the animal died.  A starting dose is usually based on previous data or experiment , if no data is available to have a preliminary estimate of the LD50 as per OECD (Organization for Economic Cooperation and Development) 425  starting dose of 175 mg/kg with a dose progression of factor 3.2 will yield the best result.

If the substance is more likely to have a low toxicity  a limit test can be done before proceeding to the main test.  Limit test is done by giving  1 animal  a dose of 2000 mg/kg if the animal die the main test shall be conducted but if the animal survived within 48 hours four additional animals shall be sequentially dose. If more than three (3) animal died you need to proceed to the main test but if three (3) animal survived it means that the LD50 is above 2000 mg/kg and the main test is not anymore necessary.

Conduct of the main test

The dose that should be given to the first animal should be a step below the estimated LD50. If the animal survived after 48 hours and there are no signs that the  animal would die then the second animal will receive a higher dose ,if it dies the third animal will receive a lower dose (same as the first animals’ dose) but  if the second animal survived  the third animal will receive a higher dose. This cycle will continue until it meets one of the following stopping criterion.

  1. 3 consecutive animals survive at the upper bound;
  •  5 reversals occur in any 6 consecutive animals tested;
  •  at least 4 animals have followed the first reversal and the specified likelihood-ratios exceed  the critical value.

For a more detailed test and computation read the OECD   Test Guideline 425.

This procedure involves animal manipulation and most countries have set of rules regarding these kind of test, so before conducting such procedure be sure to adhere to all rules or law of your land. For reference, most countries requires that the procedure be reviewed by an entity commonly called as  IACUC or Institutional Animal Care and Use Committee. The group is composed of expert which are connected to the instituition/company on which the test will be conducted. They will review the protocol shall give recommendation and approval whether the said test/procedure can be conducted.

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