Phentermine
Phentermine is a natural monoamine alkaloid derivative and a sympathomimetic stimulant with appetite suppressant property. Phentermine, which was part of the Fen-Phen anti-obesity medication, stimulates hypothalamic release of norepinephrine, a neurotransmitter involved in stress responses (fight-or-flight reactions), and reduces hunger sensation. Phentermine also causes the release of epinephrine or adrenaline outside of the brain, resulting in breakdown of stored fat.