These drugs decrease appetite or increase the feeling of being full, the NIDDK says. They do this by increasing one or more chemicals in the brain that affect mood and appetite. Phentermine (Fastin, Adipex-P, Pro-Fast and other brand names) and sibutramine (Meridia) are the most commonly prescribed appetite-suppressants. Other appetite suppressants are diethylpropion (Tenuate) and phendimetrazine (Bontril, Plegine and other brand names).
Side effects of phentermine, phendimetrazine, and diethylpropion can include sleeplessness, nervousness and euphoria. These drugs may aggravate existing heart disease, high blood pressure, an overactive thyroid gland or glaucoma. People with these conditions should not take these medications.
Sibutramine can be used for up to two years. Side effects of sibutramine include an increase in blood pressure and heart rate. These are usually small increases, but people with high blood pressure, heart disease, irregular heartbeat or history of stroke should not take sibutramine. All people taking it should have their blood pressure checked regularly.
(Amphetamines also suppress appetite, but because of the potential for abuse and dependence, they are NOT recommended as weight-loss drugs.)