I also have a cat that has chronic URI's. Ask the vet about Zythromax. It's a pediatric antibiotic that works very well on URI's. Also, Orbax & Interfon. Those are the two things that have helped Mollie Rose tremendously!

I also give Mollie Rose a vitamin supplement that helps boost her immune system, called Lysine. I give her a 1/4 tab of 500 mgs each day.

Good luck!