Metacam is not approved for use in cats in the USA except the ONE TIME shot (as described in the link I posted earlier) Of course we all know vets dispense medications off label, and in many cases I am okay with this. But not for metacam.
In Europe, metacam is approved for feline use and is manufactured and dispensed in feline doses. In the USA doses have to be broken down based on dog doses. Usually they are made up into premeasured syringes for the pet owner to dispense, to avoid the pet owner making any mistakes, but there is always room for error when the doses are being figured. And there is always room for error when the pet owner is giving the doses too. Cats should not have metacam at ANY dosage more than once every two days.
But I'll stick to my opinion that cats should not e given metacam ever, with the exception of nothing to lose situations, where quality of life for whatever life is remaining, is the only concern.