There are many ways to stimulate appetite in a dog or cat.
Mirtazapine has the side effect of stimulating appetite and can be a good choice. It performs well in clinical trials and seems safe. It’s the one I’ve used in the past. Mirtazapine can antagonize the beneficial effects of Zofran / Ondansetron so there are times that Capromorelin is better.
Entyce Capromorelin (brand name: Entyce®) is a branded product that uses a different, “intentional” pathway to stimulate appetite. It increases a hormonal precursor to “ghrelin” but also increases an ‘insulin-like-growth-factor’ that was linked to cancer formation in people. No such relationship is known in animals.
Honestly, I’d use either one. I think I’d let price do the talking.
For chronic Kidney Disease cases where probiotic and nitrogen-reducing microbes are a thought please see…. https://drjohnson.com/azodyl