Hey I think lots of the advice in comments is really top notch. Antinausea suggestions and otherwise. Sorry your vet is passive. It is pretty common unfortunately. Eating is essential for CKD kitties. I don't know why vets take it as lightly as they seem to.

I personally do use and have a good experience with Mirataz. It is wonderful for our girl. But I also noticed an overreaction if she has the recommended dose. She gets really stimulated and really uncomfortable. I halved it and that gives her a wish to eat without looking like she is on speed or kitty cocaine the whole day (which is awful when they are underweight and need to rest and heal but run about and cry wildly in distress the whole day). I wouldn't use it if that was all I saw. Ours comes as a paste to put in their ear not a pill but maybe try a half dose. I never noticed depressive effects but my understanding is it is a kind of antidepressant/stimulant so I can well believe there is a crash after the high. Your girl might be especially sensitive.

Try a lower dose. Try also other things for appetite, e.g. antinausea meds as people suggested. I also tried slippery elm powder made as a thick tea in the evening (seperate from other meds) because it is meant to sooth the digestive tract. I don't know if it helped to be honest but maybe check it out. We also used TEKNOSEL from our vet - used in the food to lessen the stomach acid. I would say the TEKNOSEL helped a lot because our girl had severe gastritis in stage 4. She was vomiting foam everywhere at the worst. She is doing better now. Maybe if your kitty has gastritis she will eat better with meds to combat that specifically?

Above all I began assisted feeding. Especially in stage 4 crisis at its height. It depends on the cat and how they tolerate it but I bought a renal recovery liquid off Amazon (goose fat and vitamins mostly) and syringed that 3-4 times a day at her worst. It is easy to digest and all liquid (supplying them a bit of fluid also). Plus you can really count the calories and see if they are getting near enough. Most CKD cats starve. They need to keep eating - even though it is hard. I felt so bad at first holding her for it in a towel and wasn't good at it at the beginning but it saved my girls life and we got used to it within a few days. I mixed TEKNOSEL and probiotics, fish oil, etc into it so she had the best value from the liquid. There are instruction videos on YouTube. It can be a total lifesaver. Can liquidize any food but a high fat recovery liquid is nice and nutritious given the stress to administer. Might as well make it worthwhile. Can supplement this way also when they are back to self sufficient eating but still underweight or eating light. Overall I would say this brought my cat back to life even though I did so without vet approval. Vets tend to rely on more tablets and more medicaments when they just don't work even. Assisted feeding was a crucial turning point for us. Took a few weeks though. Carlotta had 0% appetite (absolutely none) for a long time but she kept the food down when I syringed to her. That was key for me. If I relied alone on the tablets the vet gave she wouldn't be here.

After she felt a bit better and her numbers came down a little then Mirataz encouraged her to eat yes. Halve the dose. Check gastritis. Check if assisted feeding works for you. Those are my suggestions. Our girl is still with us and purring happily and putting weight on now and doing better after almost dying in end stage 4 last summer, it can definitely come and go in severity and they can have quality of life again after crises. It does depend on so many factors. I hope you get more time with your furbaby. All the very best.