How long has he been on it? If he's been on it for a while, you might want to ask your vet about adding Tramadol to the mix. The link I posted above has lots of ideas on what you can do to relieve their pain. I have been in your shoes a lot, I had a great dane who needed a hip replacement surgery by age 1, however we could never get him healthy enough to go through surgery and he died due to other health issues at 18 months.cprcheetah, the vet prescribed Rimadyl, but it does not seem to be working! Now he's just lying down and refusing to stand even to eat. He tries to stand up, howls terribly in pain, so he gives up and tries to catch his breath. I gave him Rimadyl, but the pain seems to worsen. I can't bear it, I feel so helpless. His crying is so painful to hear.