I would say any human medicine is for exactly that... for humans only. Any usage of human medicine on any other species probably hasn't been widely tested. I doubt many humans would be willing to take medicine/drugs that were originally created for a dog/monkey/giraffe/fish without first consulting a doctor.
Any direction of use of human medicine should be given from someone with direct knowledge of the situation and has the training and/or background to make educated decisions (i.e. veterinarian)
Since drugs and compounds may behave differently in animals than in humans, veterinarians should ask compounding pharmacists if they have specialized training or credentials in veterinary compounding, and veterinarians should specifically seek the compounding services of pharmacists who have specialized knowledge of veterinary compounding.