ABSTRACT
Toxicologists have debated for many years the wisdom of extrapolating the results of toxicity tests in rats (and other species) to humans. The debate usually centres upon whether a particular species is a good model for people. The conclusion of such debates is generally that the only real test for toxicity in humans is to use ourselves in the toxicity test. This, of course, raises significant ethical problems and therefore a compromise has been struck whereby a battery of toxicity tests using different animal species is used for assessing the safety of a new drug and the tests are crowned with carefully controlled clinical trials when the toxicologists have no reason to believe that the drug will cause the volunteer or volunteer patient any ill effects. It is therefore necessary to finalise the toxicity testing of a new drug with a ‘test’ in the species for which the drug is intended. This rule is also true for veterinary medicines, although in this case the ethical situation is different and it is considered appropriate to test the drug in the target species very much earlier in its development programme than is the case for human medicines.
