You can't walk out of this room with the veterinarian in this near-homicidal state. You'd have to turn your back on him. He'd get the drop on you. Surely he would harm you or your dog in his violent mania.
With your dog clutched to your breast, you reach out with your free hand and grab a syringe of dog medicine from the cabinet. You grab the biggest syringe of dog medicine that you can reach and you lunge. Roaring you plunge the syringe into the veterinarian's neck and empty its contents. The veterinarian staggers back, grabbing his neck.
He curses, and then he laughs, tossing the syringe off to the side and choosing a horse scalpel from the counter. You realize your mistake. This guy's a veterinarian. Of course he's immune to dog medicine.