ABSTRACT
Toxicity testing in the early phases of drug development has three main purposes: to demonstrate toxic effects and the circumstances of their occurrence; to show what toxic effects did not occur; to suggest whenever possible the likely mechanisms of toxicity. The toxicity testing of a candidate medicine is not an exercise in pure science and logic. Administration of a drug by a particular route may entail additional studies to examine both the local and systemic consequences of use of that route, e.g. topical toxicity tests by inhalation or of the skin, eye, rectum or vagina. Carcinogenicity testing resembles chronic toxicity testing but done over a much longer period, because tumorigenesis requires many months, even if potent compounds are involved. Toxicological assessment is marked by the breadth of knowledge required and essential need to correlate its findings with related branches of experimental biology and clinical medicine in ensuring safe, usable medicines, and better understanding of bodily mechanisms of health and disease.
