Faced the same sort of dilemma a few years back when my cross breed dog, Molly, was so obviously in pain. She had been my faithful companion for 15 years and i just did not want to let her go. I did ask the vet if there was anything she could prescribe which would ease Molly's pain. The vet told me that my poor dog was riddled with arthritis and had also fallen victim to a disease older unspayed dogs can get which had affected internal organs. She advised me to let her go, which i did. About 18 months later, i got another dog, a Jack Russell. And, while Molly will always occupy a place in my heart, there is plenty of room there for Milo. Do the right thing for your beloved pet, Smow.