Due to diet and lifestyle change, obesity has become a more prevalent condition compared to our ancestors. Currently 66 percent of Americans are considered overweight, according to Weight-control Information Network, a branch of the National Institutes of Health. Weight-loss drugs carry inherent risks and should be used with caution. Note that sibutramine, or Meridia, was approved in 1997 but was banned in 2010 because follow-up studies indicated serious heart events, according to MayoClinic.com.
Appetite Inhibitor
Most weight-loss prescription drugs are appetite suppressants, including phentermine, diethylpropion and phendimetrazine. Phentermine is the most commonly prescribed variety among them in the United States. The main point of effect of these drugs is appetite inhibition. These drugs interferes with the hormonal and central nervous systems, causing the release of norepinephrine, which is a hormone that tells the body to "fight-or-flight." As a result, a series physiological reactions take place, including faster heart rate, higher blood pressure, and reduced appetite. All of the drugs in this class are approved by the U.S. Food and Drug Administration only for short-term use, which is defined by less than 12 weeks. Any prescription longer than that would be "off-label" use, according to Weight-control Information Network.
Like all central nervous system stimulants, side effects of this class of weight-loss prescription drugs include dizziness, headache, blurred vision, confusion and insomnia, according to MayoClinic.com. In addition, phentermine has been associated with primary pulmonary hypertension, which is a rare disease of the lungs. Although the incidents reported involved other drugs used in combination with phentermine, including fenfluramine and dexfenfluramine, it has not been ruled out that phentermine alone can cause primary pulmonary hypertension, according to Merck Manuals Online Medical Library. Primary pulmonary hypertension, albeit rare, is often fatal when it occurs.
Lipase Inhibitor
Orlistat, is known as Xenical by prescription and Alli by its lower-strength over-the-counter variety. It is not an appetite suppressant. Its main point of action is in the intestine, where it seeks to inhibit "lipase", a digestive enzyme that breaks down dietary fat. The principle is that if fat is not broken down, it can not be absorbed by the digestive system into the blood stream, and therefore is removed from the body with the bowel movement.
Orlistat is the only weight-loss prescription drug on the market that is approved for longer-term use; that is, more than 12 weeks. Its safety and effectiveness have not been established for use beyond two years, however, according to Weight-control Information Network. Orlistat is meant to be used in conjunction with a reduced-calorie, low-fat diet and exercise. Its side effects include diarrhea, frequent stools, gas, oily spotting and trouble controlling bowel movements, according to Drugs.com.
Anti-depressant
Some antidepressants have been prescribed as appetite suppressants, as an off-label use, according to Weight-control Information Network. These include bupropion, topiramate, zonisamide and metformin. The effect of these drugs, however, tends to be modest, and patients usually regain weight even when they are still on the medication.
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