Phentermine (α,α-Dimethylphenethylamine), a contraction of "phenyl-tertiary-butylamine", is a psychostimulant drug of the substituted amphetamine chemical class, with pharmacology similar to amphetamine. It is used medically as an appetite suppressant for short term use, as an adjunct to exercise and reducing calorie intake. There are various formulations phentermine as a single agent available under many brand names, in many countries.