Celecoxib is also an NSAID yet it works by blocking cyclooxygenase-2 (or COX-2), an enzyme that sends pain messages. (NSAIDs like ibuprofen and naproxen, on the other hand, block COX- 2 and COX-1 enzymes). Researchers found that men and women who took celecoxib raised their stroke risk by a staggering 69 percent. That’s very bad news indeed when you consider Celebrex is one of the best-selling drugs in America!