be aware that the livestock and pet meds have differing pH levels based on their needs. if it differs from humans, and most do, there is a strong possibility of developing abcesses at the injection site as your body tries to fight off the meds. fish antibiotics are neutral pH as they are designed to be placed in the water.
that said, i do know alot of older horsemen who use some oral meds available for horses with no issues, but the pH abcess info came from a friend of mine who is a vetrinarian.
"Only the dead have seen the end of war." - Plato