As of 2015, diet pills that the U.S. Food and Drug Administration has approved include Contrave, which combines bupropion and naltrexone; Qsymia, which combines phentermine and topiramate; and Belviq, which is lorcaserin, according to WebMD. Although the three weight-loss drugs function similarly, all of them may not be right for everyone. Contrave's packaging warns that bupropion, an antidepressant marketed as Wellbutrin, increases the risk of suicidal thoughts.
The FDA approved Contrave, which removes food cravings and feelings of hunger, in 2014 but required the drug's manufacturer, Orexigen, to conduct an additional study to show how the weight-loss drug affects the heart, explains WebMD. Experts do not understand fully how bupropion and the anti-addiction drug naltrexone interact to be effective. They believe that naltrexone blocks certain brain receptors to curb cravings, while bupropion reduces the appetite.
Researchers do not understand exactly how Qsymia, which the FDA approved in 2012, works. It may have an impact on the brain, increase the quantity of energy the body uses or decrease the appetite, notes WebMD. The diet pill contains the appetite suppressant phentermine and the anticonvulsant topiramate.
Belviq, also approved in 2012, affects the brain's hunger receptor, and patients experience fullness sooner as a result, according to Belviq. Scientists cannot explain the way in which the drug achieves the result. Side effects of the weight-loss drug include slowed thinking, memory changes, heartbeat and heart valve problems, and painful or prolonged erections.