Looking into why Merck's painkiller drug Vioxx increased the risk of heart attacks, researchers from University of Pennsylvania's Perelman School of Medicine found that it was suppressing the production of enzymes vital for the protection of heart.
Vioxx was withdrawn from the market by Merck in 2004 after studies showed that it more than doubled the risk of heart attacks and strokes among those who took the drug.
Vioxx belonged to a new class of painkiller drugs that worked by blocking the production of a single enzyme, Cox-2. This enzyme was responsible for the production of molecules that caused pain.
However some of the molecules were responsible for protecting the heart, including breaking up clots and promoting blood flow into the organ.