Hi michala,   Thank you for your question! Pseudoephedrine is a decongestant. It works by making the swollen blood vessels in the nose smaller so that you can breathe easier when you have a cold or sinus infection. Ephedra is probably what you're thinking of in regard to the diet pills. The FDA banned use of ephedra in 2004 after several reports of death due to heart problems caused by supplements containing ephedra. Prior to 2004, ephedra was used in several diet pills, as it works by speeding up the body's metabolism. The problem was that ephedra also sped up the heart, leading to heart attacks in certain people. You can read more about ephedra at http://www.fda.gov/oc/initiatives/ephedra/february2004/. I hope this helps clear things up!   Best of luck, Casey