Phentermine is a prescription medication primarily used as a short-term treatment for obesity. Classified as a sympathomimetic amine, it works as an appetite suppressant by stimulating the release of neurotransmitters in the brain, specifically norepinephrine, which helps to reduce hunger and increase feelings of fullness. Phentermine is typically prescribed alongside lifestyle changes such as diet and exercise to aid in weight loss for individuals who are overweight or obese and have associated health risks.