VPT 311: General and Systemic Veterinary Pharmacology (2+1)

Preclinical safety and toxicity testing

PRECLINICAL SAFETY AND TOXITY TESTING 

• All drugs are toxic at some dose. To correctly define the toxicities of drugs and the therapeutic index comparing benefits and risks of a new drug is an essential part of the drug development.
• Most drug candidates fail to reach the market, due to the limitations of toxicity.
• Lead drugs that survive the initial screening and profiling procedures must be carefully evaluated for potential risks before and during clinical testing.
• Although no chemical can be certified as completely "safe" (free of risk), the objective is to estimate the risk associated with exposure to the drug candidate and to consider this in the context of therapeutic needs and duration of likely drug use.
• Toxicity testing is time-consuming and expensive. Two to six years may be required to collect and analyze data on toxicity and estimates of therapeutic index before the drug can be considered ready for testing in humans.
• Large numbers of animals may be needed to obtain valid preclinical data. Owing to the situation arising out of concerns of animal usage, animal testing has become a public issue and some segments of the public attempt to halt all animal testing in the unfounded belief that it has become unnecessary.
• Extrapolations of therapeutic index and toxicity data from animals to humans are reasonably predictive for many but not for all toxicities.