Cyclooxygenase-2 (COX-2) inhibitors selectively block the COX-2 enzyme and have been used to treat OA and RA with a low risk of adverse gastrointestinal effects.10 Blocking this enzyme impedes the production of prostaglandin (PG) E2, which is often the cause of pain and swelling during inflammation.11 PGs are enzymatically derived metabolites of polyunsaturated fatty acids, such as arachidonic acid. Here, PTGS2 is linked to rheumatoid arthritis.