Popular pet painkiller has serious side effects 11:19 PM CST on Friday, February 11, 2005 By JIM DOUGLAS / WFAA-TV Not long ago King Billy the Golden Retriever was so stiff with arthritis, a veterinarian said to put him down. "He had so much life in him I said I just can't do that." So owner Vince Sharkey put his old pal on a non-steroid painkiller called Rimadyl. "Before I had him on Rimadyl, he was not even able to walk," Sharkey says. "He would drag his back half of his body. The moment we got him on Rimadyl, he...