Vioxx is an new class of Non Steroidal Anti-Inflammatory called Cox2 inhibitors. It reduces inflammation and thus pain. It is thought to be less hard on the stomach than previous types of NSAIDs like, Aleve, Relafen all of which cause stomach bleeding. Vioxx can cause some water retention and often ankle swelling and can effect your kidneys over time.

I think you are supposed to be on it for a while or untill you heal. Not sure what Costo is or how long it lasts.