There are two types of Metacam - a canine and feline version. The canine one probably shouldn't be used on cats, and I expect this is what your brochure was referring to.

I have used the canine version on a rat before. Metacam is basically a steroid alternative, and as steroids are used on a wide variety of animals, Metacam should be safe in all respects too. In all the surgeries I've been gaining experience in, 99% of the time Metacam is prescribed as an anti-inflammatory to ease joint and muscular pain.

I wouldn't panic about the Metacam - it has far less side effects than any steroids you could be offered!