Im very concerned that uour vet is giving both a nsaid (non steroidal anti immflamatory drug) in conjunction with a steroid. They should not be given together. Also, if you see any possible adverse reaction (not eating, vomiting, LB issues, drinking more/less) than you need to stop the nsaid immediately and re evaluate.
Im at work, typing on a phone...so cant be too lengthy. PLEASE look at the link in my signature and read through some of it. Also there is a link (sticky/announcement) from rebecca on nsaids...at the end of the article is an information sheet you really should read as you decide to continue the use of any nsaid (which is what metacam is)