First approved in America as long ago as 1959, Phentermine is an appetite suppressant in the amphetamine and phenethylamine class.

Interestingly, the exact way in which drugs like Phentermine work is unknown, although scientists assume it works on the centers in the brain that control appetite in order to make you feel less hungry. In addition, Phentermine will stimulate your nervous system, causing a rise in both blood pressure and heart rate.

This is a prescription only drug that is usually used for the short term treatment of extremely obese individuals with risk factors for heart disease. It should never be combined with other weight loss medications, but to be effective is combined with an appropriate diet and exercise plan.

Short term use is usually considered to be less than 12 weeks, based on the belief that it loses its effectiveness as an appetite suppressant as the body adjusts to it. However, research has shown that it is still effective for up to 36 weeks.

Due to the stimulatory nature of this drug, it is generally recommended that you take it early in the day (before or after breakfast) to reduce the risk of insomnia.