If you are filling veterinary prescriptions and you have questions or concerns about the drug prescribed, it is important to contact the veterinarian for clarification. Lowering or raising the dosage or substituting medication may seriously compromise an animal’s health. Do not make changes to veterinary prescriptions without first contacting the prescriber because drugs affect animals much differently than humans. After contacting the veterinarian, clarification or any changes made to the original prescription should be documented on the back of the original prescription.
Source found at Kansas Board of Pharmacy March 2013 Newsletter