Like Jen said, many of the Rx are human meds. I got Chi's doxy at Walmart for several years before the dramatic price increase. Doxy is the #1 treatment for Lyme disease in humans as well as pets. Now I'm getting it through a compounding pharmacy that is making it for less than I can get anywhere else, and it is a pressed tablet, flavored, and scored for proper dosing too. Win-win-win for me and I don't have to hide it in food or coat it with PB or cheese. Her eye meds are also compounded. I get a much larger quantity of cyclosporine that that stingy little bit that came from the vet! Those compounding pharmacies are both for humans, and Chi's label says ChiChi The Dog Lathrop. Walmart used to ask me to confirm her birthday for security purposes.
If you get any of the catalogs like Fosters & Smith, or are familiar with places like 1-800-Pet-Meds and Allivet, those have non-Rx products and also Rx products. I mentioned the heartworm meds for mom's dog, and that required that the vet either call in or fax the Rx, and then we called in to pay. It was all very easy.
To Jen - my old vet (I'm trying hard to never mention her again) refused to give me an Rx to take to my human pharmacy. She and her staff also gave me a very hard time about me purchasing Dasuquin over the internet. Five years ago, old vet was charging about double the price I could purchase the Dasuquin from Allivet. No wonder that office was giving people a hard time; that's a very nice markup! Well, instead of continuing to benefit by ripping me off through her bullying tactics and excessive vaccinations, she lost a lifetime of revenue from 4 patients that is now 5! That time when ChiChi was so sick with the autoimmune flareups in 2009, I was in that office almost every week, sometimes more than once a week. She lost out big, and I'm happy about that every time I think of it. Karma!