Taxim is an antibiotic, if it doesn't worth then it's possible the bug the dog's caught is a virus
and not a bacterial infection (since antibiotics
DO NOT fight viral infections), something like a flu, in which case... heat, water, food, rest.
It's also possible it's unrelated to any infection. Some breeds of dog (such as the pug and the bulldog) have a very flat face which means their soft palate is pressed back into their throats causing all sorts of respiratory problems.