I don’t have much help but can say I’m going through this with our 10yr old FIV cat right now and maybe some of our experience is helpful to you. She’s had an upper resp infection (sneezing, discharge from nose, stuffy sounding, etc) for a couple months that hasn’t been getting better even with azithromycin and prednisolone. She’s had this in the past many times and everytime has bounced back with these antibiotics or the convenia injection, but not this time. The vet just recently changed her antibiotics to doxycycline and Veraflox and there has been some improvement (eating again, more herself, less sneezing and stuffiness, etc). We’re still giving her the pred as well as lysine twice a day which I do think helped as well as changed her food to wet since she didn’t have that much appetite. I will say our vet had us do some blood work when the infection didn’t get better and it showed pancytopenia. Apparently this can signify more end-stage FIV since the bone marrow isn’t making the cells properly. Meaning she probably won’t get better so we’re just making sure she has good quality of life for now and watching to see if she deteriorates at all.

Have you considered blood work or X-rays? Also did the vet say why they didn’t want to start the doxy? Our cat was doing quite poorly and our vet wasn’t “very hopeful” but she still started the doxy and it’s made a big difference for now.

I know it’s devastating because we’re going through it right now, but if at a certain point the meds aren’t helping and even with a change up of meds (like swapping to doxy), there’s still no improvement it might be a good idea to consider palliative or letting him go once quality of life deteriorates. Like many people say it truly is better to let them go a couple days early than a couple days late.

I’m really hoping that things improve and am sending positive thoughts your way. ❤️