I put my nearly 11 year old Tiffany on to Cystease (same as Cystaid but cheaper and easily obtainable online) after a couple of bouts of cystitis, and after 5 years she's only had one recurrence, when I tried stopping it, and I just upped the dose for a couple of weeks to knock it on its head
she has one every other day, sprinkled on her food (the capsules are easily opened) and must be totally without taste or smell, as she has never refused it
if you decide to try it, I would suggest you start with two capsules a day, for 14 days, then reduce to one a day for the next 14 days, then one every other day if they have done the trick - but be ready to go back to the beginning at the first sign of a symptom - it took me two cycles of this regime to get Tiffany stabilised
Cystease is a supplement, not a drug, and can be given indefinitely, as no bad side effects have been recorded