Officials at the U.S. Food and Drug Administration (FDA) are investigating reports that the action of the commonly used blood thinner Plavix can be neutralized by some heartburn drugs. Because Plavix can cause stomach upset, patients are often prescribed proton pump inhibitors such as Protonix or Nexium along with the drug. But researchers have found that patients taking Plavix and these heartburn drugs have a significantly increased risk of hospitalization for chest pain, heart attack, or...