That’s great thanks so much for all of the advice @Wiebke thats made it so much clearer for me to understand. So definitely ok for me to give him 2ml of the cystease/water in one go in the evening and that isn’t too much for him? He doesn’t enjoy the mixture but is a very well behaved boy and takes it with little fuss!
No, that is not too much for as long as he has acute symptoms. I would see whether you can reduce it to 1 ml when things settle down in between between flare ups but that is part of longer term management, working out how little you can get away with and how much he needs to be as comfortable as possible. Ideally the time between acute episodes will eventually lengthen and the IC will fade on its own in its own time. The good news is that is not deadly and not life-shortening unless you are dealing with the most extreme form.
My Nerys (the big piggy in my avatar picture on the left) had it for 3 years and then lived another 3 years without any bladder problem whatsoever, dying from age related issues at 8 years old. She was my first IC piggy when glucosamine was still a rather new thing to do and IC wasn't well known.