Horsegal beat me to it. My cat’s arthritis is night and day with Cerenia vs without it. I’ve done the experiment several times of putting her on, taking her off, putting her back on, and it really does make a difference. Without it, she is visibly lame at the walk on her RF (her R elbow radiographs are not pretty). My cat is like the OP’s - it takes divine intervention to give her oral meds repeatedly, as she remembers her grudge after a couple doses and does the alligator roll while biting and struggling, and she also will not eat treats if she is at all suspicious of something going on - so I use the injectable Cerenia, diluted in saline and given SQ. I currently give it 3-4 times per week; the most that you want to give it is 5 days in a row, then 2 days without, because continuous use can cause side effects due to disruption of dopamine signaling in the brain.
My cat is also on Adequan every few weeks and got the loading dose again this past winter. I don’t think it’s making as much of a difference as it used to, now that her arthritis is more advanced, but I have been happy with it in the past (she is my third cat that I have had on Adequan). Adequan is also cheap when you’re using cat-sized doses and extremely safe. While it’s labeled for IM use in dogs and horses, and some people use it IM in cats, the unofficial scuttlebutt from the vets who recommended Cerenia to me is that Adequan works just fine when given SQ to kitties, and that’s how I’ve used it in the past.
I should note that neither of these practices is supported by much in the way of actual research, and they are definitely off-label uses of these drugs.