Working at a vet's office I know all about Metacam. Although there are risks, you need to outweigh the risks versus benefits. This new label is nothing new as far as information goes. It is just stating the obvious. It has always been off label use and has always been a little risky for cats. However, if your cat has been on it this whole time and you have seen no side effects it may suit him better for you to continue using it. Cosequin works very well but takes awhile to kick in. If prednisone is the steroid he is referring to there are a lot of side effects to this steroid, including effects on appetite, water weight gain, an increase of urination and urinary incontinence etc. If all you are worried about is pain perhaps you can ask your vet to prescribe you some liquid ketoprofen?