Mydog has been on Deramaxx for about 2 weeks--he has lost his appetite and is very listless. I just awoke in the middle of the night and found him panting like he had been exerting himself greatly and his heart beat seemed extremely fast. He is 13 and has been pretty healthy until the last three weeks or so with the exception of some stiffness from arthritis. The loss of appetite and listlessness have occurred since he's been on Deramaxx. I've read about the side effects of Deramaxx, so I'm really worried. What can I do?

