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Toxicology services:
Acute Toxicity Acute Toxicity
Acute toxicity describes the adverse effects of a substance which result either from a single exposure or from multiple exposures in a short period of time (usually less than 24 hours). To be described as acute toxicity, the adverse effects should occur within 14 days of the administration of the substance.
Subchronic Toxicity
Subchronic toxicity studies with rodents are generally conducted for 90 days (3 months), but they may be conducted for up to 12 months. Results of these studies (1) can help predict appropriate doses of the test substance for future chronic toxicity studies, (2) can be used to determine NOELs for some toxicology endpoints, and (3) allow future long-term toxicity studies in rodents and non-rodents to be designed with special emphasis on identified target organs.
Chronic Toxicity
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Chronic toxicity studies provide a thorough examination of the dose effect of a given substance on homeostasis, bodily function, induced diseases, and the effect on lifespan. Chronic toxicity studies provide the bulk of the preclinical information used for assessing safety and risk. The study is conducted in multiple species, in both sexes, and for a
duration that approaches the lifespan of the animal. These are very large and complex studies that necessitate a great deal of day-to-day management. There are multiple intermediate clinical evaluations, including daily observations, weekly food and water consumption, and body weight determinations. At the termination of the study, or at times of interim sacrifices, all animals are necropsied. |
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LD50
The LD50 (Lethal Dose, 50%) or median lethal dose of a toxic substance is the dose required to kill half the members of a tested population. LD50 figures are frequently used as a general indicator of a substance's acute toxicity.
Maximum Tolerated Dose
The maximum tolerated dose (MTD) is the highest daily dose of a substance that does not cause overt toxicity typically in a ninety-day study in laboratory mice or rats. This dose is then used for longer-term safety assessment in the same species, usually lasting two years or a lifetime. The rationale for using the MTD is to maximize the likelihood of detecting any chronic disease effects of a substance, including cancer. Using higher doses also increases the statistical likelihood of detecting the intrinsic hazards of substances.
Carcinogenicity Studies In some cases a chronic study could provide data need to evaluate the cancer potential of a certain substance, however some substances require a definitive carcogenicty study to be conducted. Cancer potential can be determined whena study is conducted in rodents and lasts for the major part of the natural lifespan of the animal. The study is generally carried out using at least two dose levels, and it is usually designed to mimic the route of human exposure.
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