Yes, a lot of the meds are the same. Some times the size is different than what you get from Doc. A lot of what we have on the shelf to Rx to dog/cats is a human drug. Doxy, Amoxi,Flagyl, Pred,... are all human drugs. Some drugs we use are animal only forms of human drugs- Clavamox is a lot like Augmentin but not 100%. And then some are animal only.
Dosing can be a lot different form animal vs. human- Benadryl is used a a higher level in dogs than humans, most human OTC pain meds are very bad for dog/cats...
If you are serious about drug info, get a PDR (
http://en.wikipedia.org/wiki/Physicians%27_Desk_Reference ) .
I am not one of those folks that say " Only a doctor can do that", but be smart and get solid info ( no just interweb experts ;joint ) before you take anything. And remember that even the safest meds can cause problems if used wrong or if you have an reaction to it.