Nonsteroidal anti-inflammatory drugs that selectively block the COX-2 receptor only tend to have fewer side effects than those that block both the COX-1 and COX-2 receptors, according to the National Center for Biotechnology Information. NSAIDs of this type include celecoxib and diclofenac.
Most NSAIDs affect both the COX-1 and COX-2 receptors as part of their mechanism of action, writes the National Center for Biotechnology Information. Blocking the action of these receptors is key to the anti-inflammatory and pain relief actions of these drugs, but blocking both receptors may cause undesired side effects. NSAIDs that are selective for the COX-2 receptor only are less likely to cause adverse gastrointestinal or cardiac events than nonselective NSAIDs such as ibuprofen.