I'd try cosequin. It's a herbal remedy for UTI's. Skinny is on it for at least 6 months possibily forever. It's working!
Online pet med place (entirelypets.com) $14.95 a box 80 capsules (our vet charges $35.35 a box). No rx is needed. 1 dose under 10 lbs 2 doses a day over 10 lbs.
We do 1x a day.
I mix it with yogart instead of with food.
It rebuilds their bladders makes them stronger.

It's worth a try for 80 days $14.95 plus $5.95 for shipping (close to it).