In vivo toxicology studies are an important part of preclinical assessment for new drugs, chemicals, and other substances. These studies involve the use of laboratory animals to evaluate the potential toxic effects of a substance before it is tested in humans.

The primary objective of in vivo toxicology studies is to identify any potential adverse effects of the substance on the animal, including changes in physiological, biochemical, and behavioral parameters. These studies can include a range of endpoints, such as clinical observations, hematology, clinical chemistry, and histopathology.

In vivo toxicology studies can be further classified based on the exposure period and the endpoints evaluated:

1. Acute toxicity studies: These studies are conducted to evaluate the potential effects of the substance on the animal after short-term exposure, usually for a few days to a few weeks.
2. Sub-chronic toxicity studies: These studies are conducted to evaluate the potential effects of the substance on the animal after repeated exposure over a period of several weeks to several months.
3. Chronic toxicity studies: These studies are conducted to evaluate the potential effects of the substance on the animal after repeated exposure over a period of several months to several years.

In vivo toxicology studies can also evaluate the pharmacokinetic and pharmacodynamic properties of the substance, which can help determine the appropriate dosing regimen and inform subsequent clinical studies.

The results of in vivo toxicology studies can help identify any potential adverse effects of the substance on the animal, and can help inform decisions about the safety of the substance for use in humans. These studies are an important part of the preclinical safety assessment of drugs and other substances, and are required by regulatory agencies before clinical testing in humans can be initiated.