Hamster pee is brown should I give it more antibiotics?

I recently took my Siberian(miniature) hamster to the vet - he game me some antibiotics I need to ad to a liter of water and he told me to give it to the hamster for four days. I know that some antibiotics can kill a hamster and that the local vets kind of feel their way around because they are not completely sure what to do with such a small rodent. All they always give it is more antibiotics. Its day 8 and it recovered but its pee is still brown indicating that it might have a urinary tract infection. She looks a little better not so lethargic any more - I have some of the antibiotics left and is thinking of replacing her drinking water with it as before for another few days. Is there anyone out there who knows if this is plausible. Just until she looks a little better? Completely heals?