Amphetamines and phentermine share similarities. It activates your brain and neural system, raising your pulse rate and blood pressure while stifling your hunger. Phentermine is used to treat obesity, particularly in patients who have risk factors like high blood pressure, high cholesterol, or diabetes, together with diet and exercise. Other uses of phentermine not covered in this pharmaceutical guide are also possible. If you are trying to get pregnant or are nursing a child, avoid using phentermine. If you have glaucoma, an overactive thyroid, serious cardiac issues, uncontrolled high blood pressure, advanced coronary artery disease, severe agitation, or a history of drug misuse, you shouldn't use phentermine.