What does "extralabel" refer to in veterinary pharmacology?

In veterinary pharmacology, "extralabel" specifically refers to the use of a drug in a manner that is not specified on its label. This can include administering the drug for a condition that it is not officially approved to treat, at a different dosage than what is indicated, or by a different route of administration than specified.

Extralabel drug use is often necessary in veterinary medicine because certain conditions might not have a specifically approved medication, or the approved options may not be effective for a particular patient. The practice is regulated by the Animal Medicinal Drug Use Clarification Act (AMDUCA), which allows veterinarians to use drugs in an extralabel manner but emphasizes the need for professional judgment and consideration of the animal's welfare.

The other options focus on different concepts: using a drug as specified on its label refers to labeled use, using multiple drugs simultaneously pertains to polypharmacy or combination therapy, and using a drug after its expiration date is a matter of safety and efficacy but not about the labeled use of the drug. These options do not encapsulate the core definition of extralabel drug use.