Adipex, Fastin, and Ionamin are all three trade names for Phentermine. Just as Tylenol is a trade name for acetaminophen, and Advil and Motrin are trade names for Ibuprofin, Adipex and Ionamin are trade names for Phentermine.
Phentermine is a an appetite suppressant. It is used for the treatment of obesity. Phentermine is a weight loss medication that curbs the appetite.