MODEL RELEASED. Celebrex capsules. Elderly woman holding a blister pack of Celebrex (200mg), a medicine used to treat rheumatoid arthritis and osteoarthritis. Celebrex contains Celecoxib, a non-steroidal anti-inflammatory drug (NSAID). Celecoxib inhibits the enzyme COX-2 which is responsible for the formation of chemicals which trigger inflammation in joints. Because they selectively inhibit COX-2 they are less likely to have damaging side effects for the stomach and intestines than other NSAIDS. However, COX-2 inhibitors may carry an increased risk of heart attacks and stroke when compared to placebo.