On December 17, 2004 a government-sponsored study linked Celebrex to serious cardiovascular problems. Researchers halted the study when it was discovered that Celebrex’s risk of causing a major cardiovascular event was two-and-a-half times greater than that for people taking a placebo.

COX-2 class action suits are brought against the manufacturer of Vioxx, Bextra, or Celebrex by a group of victims who have suffered adverse health problems as a result of taking these medications. A class action is a civil lawsuit in which one or more parties file a complaint on behalf of themselves and all others who are similarly situated, meaning they have suffered the same, or similar, injuries. When a defective product causes harm to more than one person they can file a suit together to seek compensation for their injuries.

Vioxx was voluntarily removed from the market when it became clear that some patients who took it had an increased risk of heart attack. Similar studies have resulted in restrictions being placed on Bextra. In one year Celebrex brought in $2.2 billion because of the maker's aggressive marketing campaigns. Celebrex ads claimed that the arthritis medication was safer and gentler on the stomach compared to older NSAIDS. A more recent study performed on Celebrex concluded that a "clinically meaningful" safety advantage of Celebrex over older NSAIDS had not in fact been established.