Drug manufacturers felt the earth move when leading pharmaceutical firm Merck & Co. pulled its popular Vioxx painkiller from the shelves in late 2004 due to serious health risks it posed to users. The Vioxx discovery has since led to investigations of other drugs such as Celebrex and Aleve, and the entire industry is on edge due to the inevitability of legal challenges.

At the time Merck pulled Vioxx, users of the pain-and-arthritis medicine were estimated to be at about 2 million worldwide. Vioxx had been Merck's No. 2 drug with projected 2004 global sales of $2.5 billion--nearly 11% of the company's revenues. The company was forced to remove the drug from the market after an internal study showed that Vioxx doubled the risk of heart attacks and strokes.

Industry analysts expect widespread legal battles over the Vioxx blunder, and many Americans who have relied on the safety of pain medicines say their faith has been eroded in the system intended to protect them. In some cases, longtime users of pain-and-arthritis drugs are swearing off them altogether.