Hello kitty frantic mom, I know you are worried, but your vet would not have prescribed it if he/she did not think it would be beneficial.
Benazepril is commonly used to treat BOTH heart conditions and kidney failure in cats, and I would give it to my own cat if needed.
This is from a web site concerning people, but the same is true for cats:
"Benazepril hydrochlorothiazide, brand name Lotensin®, is a medication used to treat high blood pressure (hypertension), congestive heart failure, and chronic renal failure." (from http://en.wikipedia.org/wiki/Benazepril)
Dr. T
I am a veterinarian that wants to give you an honest answer. If I helped you or your pet, please ACCEPT my answer. Thank you!