INTRODUCTION
There is substantial overlap in the antimicrobial pharmaceuticals used in human and
veterinary medicine. To assist practitioners in their appropriate selection of antimicrobials,
according to the risk to human health due to the development of resistance, the
Veterinary Drugs Directorate (VDD), under the umbrella of Health Canada, has classified
drugs into four categories from I to IV3. Antibiotics that are used in treating severe
infections in humans, which have few or no alternatives, are ranked as Category I (very
high importance). Category I drugs are meant to be used sparingly in order to preserve
their efficacy, and are considered “last resort” treatments for severe infections in humans.
This category includes some important veterinary drugs such as ceftiofur, a third
generation cephalosporin. While ceftiofur is not used in humans, it is closely related to
some critical human drugs. Ceftiofur is approved for use in several food-producing animal
species. Due to the fact that ceftiofur has no milk withdrawal time, it is widely used to
treat mastitis, lameness and respiratory disease in dairy cattle.
There are some vet \