Study: Heart drug Tredaptive is ineffective (CBS News) The drug maker Merck said Thursday that a drug that was supposed to prevent heart attacks has serious problems. It is now warning doctors overseas to stop prescribing it. The study looked at a drug, called Tredaptive, currently used in 40 countries. Its main ingredient is a vitamin called niacin, which raises so-called "good cholesterol" or HDL. Tredaptive also contains a drug to reduce side effects. While Tredaptive is not available in the U.S., over six million prescriptions are written a year for niacin alone to raise HDL. It was hoped doing so would reduce heart attacks and strokes. The study showed that it did not prevent those problems. Cardiologist Dr. Steve Nissen of the Cleveland Clinic has prescribed niacin for years. "It raised the good cholesterol, it lowered the bad cholesterol," he said. It didn't improve clinical outcome. That is a stunning finding. More than 25,000 patients at high risk for heart problems took part in the study. Besides being ineffective at preventing heart attacks, Tredaptive caused significant side effects FDA: Praxada may cause problems for people with mechanical heart valves Merck, the maker of Tredaptive, would not specify what those side effects were. They recommended that no new patients start taking the drug, but stopped short of saying current patients should come off it. "It's an agonizingly difficult question that physicians around the country and around the world are going to have to deal with their patients over the next few days and next few weeks," said Nissen. I spoke to the chief medical officer for Merck and he would not tell me what those side effects were. He said they were still analyzing the data and had given all of the information to the FDA. It might not be until March that people get the full report. What that does is leave doctors with trying to figure out what exactly are those side effects that they are supposed to be looking for in the patients who are still taking niacin.