The U.S. Food and Drug Administration (FDA) has sent warning letters to five companies for product misbranding because the dietary supple- ments they sell containing Acacia rigidula also contain an unapproved stimulant, beta-methylphenylethylamine, or BMPEA. The Acacia rigidula plant does not naturally contain the stimulant, which has been classified as a doping agent by the World Anti-Doping Agency. Studies have shown it to raise blood pressure and heart rate and act like an amphetamine. The letters were sent to Hi-Tech Pharmaceuticals, Tribavus Enterprises, Train Naked Labs, Better Body Sports, and Human Evolution Supple- ments regarding products that include Fastin™-XR, Lipodrene®, Sudden Impact, Core®  Burner, and Phoenix Extreme.