A pharmaceutical company must show the drug’s safety in a series of laboratory tests before it can be administered to patients. This is known as toxicology. Toxicologists working for regulatory agencies typically determine the exact purpose of these studies before giving approval for the drug to be used in humans. Toxicologists compile all toxicological data and send it to a regulatory agency for approval until the organization is confident that the medication is successful in treating the disease, that any toxicity is minimal enough at therapeutic levels, and that the drug is likely to be commercially viable. The medication will then be marketed for general use in patients if approval is given. Toxicologists are needed at all stages of drug production. Their advice will help weed out chemicals that aren’t safe enough to use as medicines at each stage:

• Computer models can be used early in the drug development process to predict toxicity based on knowledge of the intended target and chemical structure, as well as current knowledge of the chemical’s or related chemicals’ properties.
• In vitro Screening tests will easily establish if a potential new drug can cause skin or eye irritation or damage DNA after chemists have synthesized it.
• Toxicologists will use computer models and in vivo experiments to figure out whether a drug’s metabolism would have an effect on its toxicity.
• If a promising candidate drug has been identified, it must be thoroughly screened for toxicity, which also necessitates the use of animals. Toxicity must be determined in the blood and tissues of animals that have been exposed. It may also be important to assess whether the drug may cause cancer or is likely to cause developmental or reproductive toxicity, such as effects on fertility or birth defects, later in the drug development process.
• To further examine any toxicity, it may be appropriate to design specialized studies. Biochemical, immunological, molecular, and microscopical methods are often used in these studies.

Toxicologists compile all toxicological data and send it to a regulatory agency for approval until the organization is confident that the medication is successful in treating the disease, that any toxicity is minimal enough at therapeutic levels, and that the drug is likely to be commercially viable. The medication will then be marketed for general use in patients if approval is given. And with all of this research, rarely an unintended side effect may be found once a medication has been licensed and is being used by a much larger population of people, many of whom may have complex health problems. Toxicologists are called in to assess whether the side effect happens and whether or not the medication can be used safely. Toxicologists are active in all phases of drug production and thus contribute greatly to public health changes.