A&B is correct that some antibiotics will take longer to alleviate symptoms because of how much the infection has invaded the body. Another item to note is that while one antibiotic is not effective, another one could be. If only one was tried, I would ask about trying another one if the symptoms worsen or become too chronic after lessening potential allergens. Worst case scenario, the URI is getting stronger because it’s not getting treated. Different antibiotics will work on different infection types. Going into Wick’s URI treatment, Wick’s vet flat-out said it’s a trial and error to see which will work, but usually it’s successful in one or two medication tries. The first medication was Bactrim for 2 weeks, with no effect. After that, we tried Baytril, which did minimize the symptoms, so we kept at it. Fast forward about a month, it was weird the symptom relief plateau’d, so Flocillin was added on top of Baytril (did not want to take it away since it was helping minimize symptoms). After one shot of Flocillin; life-changing, miraculous silence and lack of nasal discharge. Dual Baytril and Flocillin treatment was continued until my supply ran out, which was about one week after he stopped sneezing (you should keep going a bit after symptoms stop to ensure all the infection is gone). Wick’s was a particular pesky URI, so his entire treatment experiment/course lasted 3mo, though it typically never lasts that long.
Also, here’s a video I made earlier about how I administer antibiotics to Wick when he’s not having it: http://youtu.be/N12eJ5vdo4w
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.