My personal experience in using Kitty Kaviar or Wildside Salmon for over 3 years in one cat as an appetite stimulant (NOT every meal or every day, so keep that in mind) my crf fellow has not had a single UTI.
My knowledge of cyproheptadine (also called Periactin) is that this antihistamine can have undesireable side effects. I would personally, save this as a 'big gun' only to be used if no other attempts to stimulate appetite more naturally, without medication, does not work. If you'd like to know a bit more about this medication when used as an appetite stimulant and the possible side effects, click here
and decide if you want to try it.
I am on a support list where a number of cats try this, for some it works extremely well, for others it leads to side effects that are less than enjoyable for cat or human.