If patients are found to be eligible for this study and they agree to participate, they will be randomized to either receive celecoxib or placebo to be taken by mouth (as a pill) twice a day, every day for as long as they are in the study. Patients will be given a pill diary to keep track of their medications. While in this study, they will be asked not to take any non-steroidal anti-inflammatory drugs, which includes over-the-counter ibuprofen and many other available drugs. In addition, they will be asked not to take any other selective COX-2 inhibitors (the class of drug that celecoxib is).