Who determines the degree of interaction between drugs?

The degree of interaction between two drugs is based on potential clinically significant severity of an interaction when combining two drugs. It is first evaluated by a pharmacist, then reviewed by one or more veterinarians, and then—in many cases—reviewed by a veterinary clinical pharmacologist. As in many aspects of medicine, there is some subjectivity in assigning classifications, but the intent is to focus on clinical relevance as much as possible.