Izzy went like that, Angela, ie suddenly, but went on for over two more years. He was put on Fortekor, first of all and it appears that Benazecare is the same drug, benazepril hydrochloride, but by a local manufacturer. Fruise sounds like Frusicare/ Frusimide, again both names for the same generic drug.
Fortekor can take a few days to show results, whereas, if you later get, Vetmedin, it acts quite quickly (within 24 hours for Izzy ).
Have you tried Vitapet oil for the old girl ? It helped my old springer, Cindy, who got to the stage where she needed help lifting her bum, after lying down, but could manage herself afterwards. There's a special version, now, RA, with extras to help joints.
Barbara, Monty, Joly and Teddy.