Phentermine (contracted from phenyl-tertiary-butylamine), also known as α,α-dimethylphenethylamine, 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.
Phentermine may produce cardiovascular, gastrointestinal, and CNS side effects; rare cases of pulmonary hypertension and cardiac valvular disease have been reported. It should not be used by people who have a history of drug abuse, have cardiovascular disease, hyperthyroidism, glaucoma, or are pregnant, planning to become pregnant, or breast-feeding. It should not be taken by anyone taking a monoamine oxidase inhibitor. Drinking alcohol while using phentermine may cause adverse effects.
It was first introduced in 1959, and became part of the drug combination fen-phen that was withdrawn from the market in 1997 due to the fenfluramine component damaging people’s heart valves. In 2012 a different combination drug, phentermine/topiramate was approved in the US.
Different formulations of phentermine as a single agent are available under various brand names, in many countries.