Many people put them in empty gel caps. My vet did it for me so I don't know what size she used. You can order them on Amazon and someone here recently got them at the The Vitamin Shoppe.
You can cut up the pill so you can use as small of a gel cap as possible.
I had a cat that *hated* taking any sort of meds. When he got to a point where I had no choice this is what I did:-
First waited until he was deeply asleep.
Crept up behind him so his back end was towards me.
Using my body to stop him reversing, placed one hand round the front of his chest to hold him gently but securely.
With my other hand used a finger to open his mouth, then popped the tablet on the back of his tongue.
Gently held his head up and massaged his gullet and throat to stimulate a swallow response. Stayed like that until there was a definite 'gulp'.
Released his head then stroked him while observing to be sure the tablet was definitely gone.
When I was sure he'd taken it, I'd finish with an extra yummy treat.
Hope this works for you. Before I hit on this technique it was a case of chase the cat round the house then have multiple attempts to get the pill in. He'd even hold it in his mouth for 20 mins and spit it out when I wasn't looking! Always ended with stressed cat and cross me. I think the start point of deep sleep is the key.
When my boy got really stubborn I asked for a liquid version of his meds. He still didn't like it but, for him, it was easier to take syringed liquid than a tablet.
is your vet able to compound it into a liquid? my cat is on it, and i'm able to shove it into his mouth via syringe. it's not his favorite thing, but it forces him to injest it... i don't think i would ever be able to give him a pill.