Amphetamines are classified as a stimulant and function as an appetite suppressant in diet pills. The term "amphetamines" typically refers to the different types, such as amphetamine, dextroamphetamine and methamphetamine, states the U.S. Drug Enforcement Administration. While amphetamines have been used therapeutically since the 1920s, their abuse has required restriction and enforcement. All diet pills with amphetamines that are FDA approved require a doctor's prescription.
How They Work
Appetite is controlled by the brain. Amphetamines suppress appetite by increasing levels of dopamine, a chemical that results in alertness, increased concentration and registers pleasure. A study published by the American Psychological Association suggests this increase in dopamine—thus pleasure—makes food more satisfying more quickly, reducing appetite and intake. As levels increase and pleasure becomes heightened, diet pills with amphetamines can easily become habit-forming, states the National Institute of Drug Abuse.
Severe, even life-threatening, side effects can occur with diet pills. Because the mechanism of amphetamines increases bodily functions, many different parts of the body can be affected. PubMed cites side effects of diet pills—such as phentermine, sibutramine and phendimetrazine—to include increased heart rate and blood pressure, dizziness, swelling in the legs and ankles, increased urination, dry mouth, insomnia, anxiety, depression, vomiting and shortness of breath.
When diet pills are taken for a short period of time, monitored closely by a physician and coupled with lifestyle changes such as eating healthful, calorie-controlled meals and exercise, weight loss can occur. However, due to the development of safer weight loss medications, the rate of amphetamine diet pill prescription has declined.
Amphetamines have a long history of use before they were included in diet pills. According to the University of Washington, "During World War II, amphetamines were given to soldiers and pilots to keep them alert and fight off fatigue." They were originally used to treat asthma, sleep disorders and hyperactivity, states UW. According to the U.S. Drug Enforcement Administration, the first amphetamine tablet was marketed in 1937 as a nasal decongestant. Widespread use began in the 1960s, where amphetamines began being used by dieters for weight loss, according to the DEA.
According to the Weight-control Information Network, there are four amphetamine diet pills that are approved by the U.S. Food and Drug Administration as weight-loss medication and must be prescribed by your doctor. The most commonly prescribed is a combination of phentermine and topiramate, sold under the brand name Qsymia. Typically, phentermine is only prescribed for up to 12 weeks and sibutramine up to 12 months, both requiring monitoring by a physician, states WIN. Phendimetrazine and diethylpropion are also available by prescription.