NSAIDs block a group of proteins called cyclooxygenases (COX), which are involved in the production of prostaglandins and thromboxanes, which are in turn involved in inflammation. There are different types of COX proteins, including COX-1 and COX-2. Some NSAIDs block both COX-1 and COX-2. These are called nonselective NSAIDs and include aspirin, ibuprofen, and naproxen. Selective NSAIDs, such as celecoxib, block only COX-2. There is still much that is not known about how these COX proteins work.