Chronic studies on rodents (rats and mice) are needed to gauge the level of safety and toxicity of the test substance (study compound) via repeated administration over a long period covering most of the animal’s life. This kind of study yields a broad spectrum of information on the physiological, pathological and behavioural processes, revealing any carcinogenic effect and identifying any metabolites or biological markers of the test substance.

Again, choosing the most suitable administration pathway is of the utmost importance: it should aim to reproduce the human exposure scenario and the test substance metabolism in the human organism, thereby optimising results and increasing their scientific worth and reliability.
OECD Guideline 451: Carcinogenicity Studies
OECD Guideline 452: Chronic Toxicity Study
OECD Guideline 453: Combined Chronic Toxicity/Carcinogenicity Studies