The FDA approved Zetia and Vytorin in 2002 as drugs that would lower cholesterol and reduce the risk of heart attacks. The drugs have been heavily marketed and doctors have prescribed them aggressively ever since they came on the market. Yet the evidence as to their effectiveness is still not clear. In fact, Vytorin failed to clinic trials which were conducted to prove its benefits. Some doctors now believe the drugs shouldn’t be used outside of clinical trials since the evidence against using the drugs is mounting. Adding to these concerns is a potential link to cancer. According to one prominent cardiologist, the FDA set the initial standard for approval too low. “The F.D.A. set the bar too low on the initial approval,” said Dr. Steven Nissen, chairman of cardiology at the Cleveland Clinic. “It would have been a lot better if the agency had said, ‘Show us that you do more than lower LDL a little bit, show us evidence of effectiveness.’ ”