Some cats’ personalities dictate whether you can continue with treatment or whether it is more humane to put them down. I am sorry to say.
We had one cat with hyperthyroid whose high strung personality (his whole life; poor guy had probably been through a lot before we got him, we suspected) made it impossible to treat him past a certain point.

May he Rest In Peace, sweet, funny guy.
In comparison, we have an achingly calm orange tabby boy who lets me give him prednisolone every day in addition to a chemo pill two times a week. With my own fingers, I simply stimulate the side of his mouth, he opens his mouth, and I Place it as far back as I can. He always gets treats when we are finished, so maybe that helps? But that truly has bough him multiple more years of his life just because his personality is more laid back and pliable.
It just makes me sad for my first little guy, that he could not still be with us if he did not get so panicked at every attempt to help him.
