More recently, the arthritis drug Vioxx was withdrawn from the market when studies suggested an increased risk of blood clots that could lead to strokes or heart attacks. On September 30,2004, Vioxx's manufacturer Merck & Company announced a voluntary recall of the drug that was first introduced in 1999 as a pain reliever for arthritis. This was the largest recall of a prescription drug in history. Celebrex, a similar drug manufactured by Merck's rival Pfizer, had not been withdrawn as of January 2005. By all indications, both Vioxx and Celebrex had been effective in relieving the pain associated with arthritis. Both drugs had been heavily marketed by their manufacturers, and each was very profitable, reportedly earning more than $2 billion annually for Merck and Pfizer. In November 2004, the Food and Drug Administration, the federal regu¬latory body that oversees prescription drugs, announced that Vioxx may have contributed to as many as 27,000 heart attacks and cardiac deaths since it was introduced in 1999. The FDA did not order the recall, explaining that they had not yet had the opportunity to study the data related to the dangerous side effects. During the fall of 2004, allegations surfaced that Merck had received information about the greater risks associated with Vioxx a year prior to the recall. Critics charged that Merck continued to market the drug aggressively even after being advised of such risks and even advised their sales representa¬tives on how to avoid answering questions relating to side effects.