Vet reports routine use of Primor in cats

I called the Vet about my concerns with the Primor.  He says he routinely prescibes it to cats.  What are the risks?  My cat is doing well following her surgery.  She was on Clavimox for 2 weeks at first and then on Clindamycin for 2 weeks with about 2 weeks between each presription, before they took and an x-ray which showed bladder stone.  We return to office on Friday for SR and need to address this issue with vet.  

[Aleda M Cheng, D.V.M., C.V.A]

According to "Plumb's Veterinary Drug Handbook, 6th Edition", the veterinary drug handbook used in most veterinary practices,  Primor is only to be used in dogs, chickens and turkeys.