Question: to test out a new chemical (drug), what do scientists test them on first, before animaks and humans?

Lori-An Etherington answered on 15 Jun 2010:

When chemists are trying to design a new drug they are trying to model the chemical so that it will hopefully act at a specific target within the body. Thousands of chemicals might be made with very similar structures which are then usually tested on individual cell models to see if they look promising at the proposed target. Only a few of these chemicals might be interesting and are then tested in tissue taken from animals (generally rodents). The tests that are done with a chemical differ depending on what the drug is thought to do (for example the tests for a new drug for diabetes would be different from one which might help Alzheimers disease). If the chemical still looks promising at this stage it will go on to be tested for safety and behaviour in animal models. All of this testing is called pre-clinical testing and can take 3-4 years for one promising chemical, if it passes all of these tests then it can go on to clinical testing in humans (which can be another 3-4 years). If a drug is lucky enough to get through this whole process then it might be allowed to be used as a medicine in clinical practice. The whole drug development process can take 10-12 years.