Phentermine is a prescription medication often used as a short-term treatment for weight loss in individuals who are overweight or obese. It belongs to a class of drugs known as sympathomimetic amines and works as an appetite suppressant. Phentermine is thought to help with weight loss by increasing the release of certain neurotransmitters, such as norepinephrine, which reduce appetite and increase feelings of fullness.

It's important to note that phentermine should only be taken under the supervision of a qualified healthcare professional and as part of a comprehensive weight loss program that includes diet and exercise. It is typically prescribed for short-term use due to the potential for tolerance to its appetite-suppressing effects and the risk of side effects.