Phentermine is a prescription medication primarily used as a short-term treatment for obesity. It is a sympathomimetic amine, similar to an amphetamine, and works by suppressing appetite. Phentermine is usually prescribed for individuals who are overweight or obese and have not been able to lose enough weight with diet and exercise alone. It is intended for short-term use, typically a few weeks, in conjunction with lifestyle modifications such as a low-calorie diet and increased physical activity.