- Once a promising candidate drug has been chosen, it must be more comprehensively tested for toxicity; this involves the use of animals. The blood and tissues from exposed animals need to be carefully examined for toxicity. Later in the drug development process, it may also be necessary to determine whether the drug may cause cancer or is likely to cause developmental or reproductive toxicity, such as effects on fertility or birth defects.
- It may be necessary to design specialised studies to further investigate any toxicity. These experiments often involve sophisticated biochemical, immunological, molecular or microscopical techniques.
Once the company is satisfied that the drug is effective in treating the disease, that any toxicity is low enough at therapeutic doses, and that the drug is likely to be commercially viable, toxicologists then collate all the toxicological evidence to submit to a regulatory body for approval. If approval is granted, the drug can then be sold for general use in patients.
Even with all of this safety testing, very occasionally a rare unexpected side effect is discovered once a drug is approved and is then in use in a much wider population of people, many of whom may have complex health issues. Toxicologists get involved to find out why the side effect occurs, and if and how the drug can be used safely.
Toxicologists are involved in all stages of the development of the drug, and so contribute significantly to improvements in public health.