Application of Toxicokinetics in Different Toxicity Tests

The content of toxicokinetic studies in different toxicity tests, such as the frequency of exposure monitoring and characterization, can be increased or decreased according to research needs. The toxicokinetic studies of different toxicity tests are considered as follows:

(1) Single-dose Toxicity Test

The toxicokinetic results of a single-dose toxicity test are helpful for evaluating and predicting the choice of dosage form and the exposure rate and duration after administration, as well as for the selection of appropriate dosage levels in subsequent studies.

(2) Repeated administration toxicity test

The content of toxicokinetic studies should generally be included in the repeated dosing toxicity test design, which includes regular exposure monitoring and characteristic studies from the first administration to the end of the administration. The protocol used in the subsequent toxicity test can be revised or adjusted based on the results of the toxicology study of the previous test. When there are unexplainable toxicity problems in early toxicity tests, it may be necessary to extend or shorten the time for toxicity monitoring and characteristic studies of the test substance, or to revise the research content.

(3) Genotoxicity test

When the result of the in vivo genotoxicity test is negative, it is necessary to combine the exposure data to evaluate the genotoxicity
Sexual risk, especially when the in vitro test shows a clear positive result or the in vitro mammalian cell test has not been performed.
The assessment of in vivo exposure should use the same animal species, strain and route of administration as the genotoxicity test, at the highest dose or other relevant doses. In vivo exposure can be shown by the test
In vivo cytotoxicity (such as a significant change in the ratio of immature red blood cells to the total number of red blood cells in the tissue detected in the micronucleus test) or exposure (measure the exposure of the test substance and/or its metabolites in the blood or plasma, or directly Measure the exposure of the test substance and/or its metabolites in the target tissue) to prove.
If the in vitro genotoxicity test results are negative, the above methods can be used or for other purposes.
The results of the rodent pharmacokinetics/toxicity tests conducted are evaluated in conjunction with in vivo exposure.

(4) Reproductive toxicity test

The main purpose of the reproductive toxicity toxicokinetics study is to analyze the results of the reproductive toxicity test.
It helps to determine whether the different doses in different stages of the reproductive toxicity test have reached sufficient exposure. The possible differences in the dynamic characteristics of animals during pregnancy and non-pregnancy should be considered.
The toxicokinetic data can come from all animals in the reproductive toxicity test, or from some animals. Toxicokinetic data should include fetal/pup data to evaluate the test substance and/or metabolic production
Whether the substance can pass through the placental barrier and/or milk secretion.

(5) Carcinogenicity test

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