Here's a link to the veterinary compendium. Everything you ever wanted to know about anything in the animal health product world.
http://bovinemeds.naccvp.com/view_skin.php?file=index2.html
When I worked at the vet clinic the compendium was the number one reference material we used. And we used it pretty much every day. It's got every drug, every vaccine, and what it's for, withdrawal times, dosages, and anything else you'd want to know.