Phentermine is a medication that is used to suppress appetite. it is prescribed to obese people who have been unsuccessful in losing weight through diet modifications and exercise.
According to WebMD, phentermine belongs to a class of drugs known as sympathomimetic amines. It is not known exactly how the medication works, but it is believed to either decrease one's appetite, increase the body's energy or affect certain parts of the brain.
According to MedlinePlus, Phentermine is prescribed to patients for 3 to 6 weeks as its long term use can be habit-forming. This medication is available in the form of tablets and extended-release capsules.