What's the difference between human and veterinary-approved drugs?

Human drugs are just that, approved for use in humans. They are tested, formulated and designed for people. Dogs and cats, however, are not humans. That's why it's important to have medications that are approved for a species, dogs or cats. A species-approved drug is tested and formulated for that species. It also has dosing recommendations specific to that species and their weight. The safety information is also specific to the species. Sometimes it is necessary to use a human product because there may not be one that is veterinary approved.