They wont be the same, dont use them. You would rather pay a few quid more for the real stuff from the vets then have to fork out hundreds for a gastrointestinal bleed caused by human dose tablets. Dont use human antibiotics on a dog, for a start they dont kill pain they only kill bacterial infection; You wont know what bacteria your treating so the tablets you have lying around that you used for a chest infection wont work on an infected leg. The human dose will be to big too and could cause renal or liver problems, then before you know it you've nearly bumped off your prize pooch and again w