Acute Oral Toxicity test. OECD 423: 2001; EPA (Environmental Protection Agency) OPPTS 870.1100: 2002 (Office of Prevention, Pesticides and Toxic Substances, USA); Directive 92/69/EEC July 31, 1992, paragraph B.1.
Test with the Certificate of Good Laboratory Practices (GLPs).
To assess the characteristics of a toxic substance, the determination of acute oral toxicity is usually the initial step. This test provides information about the health hazards that could occur after short oral exposure. The information from an acute study can serve as a basis for classifying the substance and its corresponding labeling. The assessment of acute toxicity should include the relationship, if any, between the exposure of the animals to the tested substance and the occurrence and severity of all alterations, including behavioral and clinical abnormalities, the reversibility of the observed abnormalities, macroscopic lesions, changes in weight, effect on mortality, and any other toxic effect. The OECD and OPPTS standards include the possibility of corroborating macroscopic observations by a microscopic pathological study.
The preferred rodent species according to OPPTS and OECD Guidelines is the rat, although other rodent species may be used. In our laboratory this test is performed using mice or rats, as admitted by both the standard OECD-423: 2001 and EPA-OPPTS O870.1100: 2002. Both standards (OECD and EPA-OPPTS) are very similar in terms of the recommendation to obtain all the previous available toxicological information of the products subjected to tests or their structurally related ones; in the number of animals included in the tests, with small differences; regarding the sex of the animals; the ages and weights of the animals; the acclimatization preconditions; the maintenance of animal during the tests; the food and drink; the preparation and administration of the test substances; the administration of each dose; and results observations. Fundamentally, both standards differ in the amounts of substances to be administered to animals in the UPD (Up-and-Down) dosing scheme when a "Limit Test" or a main test is performed. When a complete main test is performed to calculate the lethal dose 50 (LD50), the EPA-OPPTS standard recommends the scheme with a progression factor of 3.2 (1.75, 5.5, 17.5, 55, 175, 550, 1,750 and 5.000 mg/kg), although when no toxicological information of the product is known, it recommends begin with the amount of 175 mg/kg. The OECD standard 423, recommends the amounts of 5, 50, 300 and 2,000 mg/kg. Both the OECD and OPPTS standards establish the UPD schemes to move from one dose to the next, both upwards and downwards according to the starting point and the estimation of the LD50. Nevertheless, in the OPPTS standard, single animals are dosed sequentially, whereas in the OECD test the animals are dosed in groups of 3 animals. The OECD standard can also classify the GHS (1, 2, 3, 4 or 5) of toxicity to which the product tested belongs. In both standards, in order to try to reduce experimental animals as much as possible, when a toxic effect is not expected, it is recommended to start with the "Limit test", performing a test with up to 5 animals and a dose of 5000 mg/Kg for the EPA-OPPTS standard, 5,000 mg/kg, and a test with 6 animals and a dose of 2,000 mg/kg in the case of the OECD-423 standard.
In general, test substances should be administered in a constant volume over the range of doses to be tested by varying the concentration of the dosage preparation. However, when a liquid end product or mixture is to be analyzed, the use of the test substance undiluted may be more relevant.
With regard to the formulation of the dosing preparation, the use of an aqueous solution / suspension / emulsion is recommended whenever possible, followed in order of preference by a solution / suspension / emulsion in oil (for example, corn oil) and then possibly solution on other vehicles. In the case of vehicles other than water, a control must be carried out and therefore the test will carry an additional cost.
It should be taken into account that the test samples will be administered in the stomach of the animals using a cannula, so the sample received must allow this type of administration.