
Seraquin consists of Inactivated yeast, glucosamine HCl, chondroitin sulphate, hydrolysed chicken protein, maize starch, saccharose, standardised turmeric extract, maize protein.
Metacalm is Meloxicam which is a NSAID which should only be given short term due the extent of the side effects
You cannot compare the two really
Carthrophen on the otherhand is a semi synthetic polymer, Pentosan polysulfate sodium (in liquid form)adminstered by monthly injections although it does have side effects they are usually far less than Metacalm. It works in a totally different way to Metacalm.
You may wish to discuss this with your vet