Weight Loss Drugs

Overview :

Weight loss medications are prescribed only as a component of a weight loss program that includes a healthy low-calorie diet and regular physical activity. On average, people on prescription weight loss drugs lose about 5-10% of their original weight. They may lose in the range of 4.4-22 lb (2-10 kg) above what they might have lost following a diet and exercise program alone. Patients who lose weight initially on a drug tend to continue to respond. However, those who fail to lose 4 lb (2 kg) within the first month on a weight loss medication are unlikely to respond to that particular drug even at an increased dosage. Over-the-counter weight loss drugs have been found to be ineffective, unsafe, or both. Most weight loss occurs within the first six months of drug use, after which the weight levels off or increases. The majority of patients regain the lost weight after discontinuing the medication. Thus short-term use of weight loss drugs may not be beneficial. However, long-term use of weight loss drugs may help maintain the lower weight. Since obesity is a chronic disorder, treatment must be continued for years or for life. However, as of 2005, sibutramine (Merida) and orlistat (Xenical) were the only weight loss drugs approved by the U. S. Food and Drug Administration (FDA) for use for more than a few weeks. Appetite suppressants (anorexiants) Most FDA-approved weight loss drugs suppress appetite by affecting one or more neurotransmitters in the brain that control appetite and mood. Various appetite suppressants increase the secretion of dopamine, norepinephrine, or serotonin or inhibit the reuptake of these neurotransmitters into the nerve cell. Some drugs affect more than one neurotransmitter. These drugs may cause a person to feel less hungry or more satiated. SIBUTRAMINE. Sibutramine was approved by the FDA in 1997 for long-term use. It reduces appetite by inhibiting the reuptake of norepinephrine, dopamine, and serotonin. One study found that patients taking sibutramine lost an average of 7-10 lb (3-5 kg) more over one year than those on a low-calorie diet alone. AMPHETAMINES OR SYMPATHIMIMETIC DRUGS. Some amphetamines are FDA-approved for very short-term weight loss. Although most of these drugs do not cause weight loss over more than a few weeks, phentermine continues to be one of the two most commonly prescribed weight loss medications—along with subitramine—in the United States. Some amphetamine-type weight loss drugs, including methamphetamine (Desoxyn), were approved by the FDA in the mid-1990s based on very little data. Other FDA-approved weight loss drugs for short-term use include: benzphetamine (Didrex) diethylpropion (Tenuate, Tenuate Dospan, Tepanil Ten-Tab), approved in 1959 mazindol (Mazanor, Sanorex) phendimetrazine (Adipost, Bontril PDM, Bontril Slow-Release, Melfiat, Obezine, Phendiet, Phendiet-105, PT 105, Plegine, Prelu-2, X-Trozine,), approved in 1982 phentermine (Adipex-P, Fastin, Ionamin, Obenix, Oby-trim, Phentercot, Phentride, Pro-Fast, Teramine, Zantryl), approved in 1959 Lipase inhibitors In 1999 the FDA approved orlistat (the first of a new class of anti-obesity drugs called lipase inhibitors) for long-term use. Orlistat inhibits the pancreatic enzyme lipase that breaks down dietary fat, which in turn decreases the body's absorption of dietary fat by as much as 30%. The undigested fat is excreted in the stool. Orlistat is prescribed for overweight or obese patients who also have high cholesterol, diabetes, high blood pressure, or heart disease Off-label use Physicians sometimes prescribe drugs for weight loss that are not FDA-approved for that purpose—so-called off-label use. The use of weight loss medications—other than sibutramine and orlistat—for more than a few weeks is also considered off-label use. Off-label weight loss drugs include: antidepressants such as bupropion the anticonvulsant drugs topiramate and zonisamide the diabetes medication metformin Antidepressants may result in moderate weight loss for up to six months after which the weight usually is regained. Metformin appears to reduce hunger and food intake and may promote small weight loss in the obese and those with type 2 diabetes. Drugs withdrawn from the market Although effective for long-term weight loss, fenfluramine (Pondimin and others), dexfenfluramine (Redux), and a fenfluramine/phentermine combination (fen/phen) were withdrawn from the market in 1997 after it was found that they caused potentially fatal complications. In February of 2004 the FDA prohibited the sale of dietary supplements containing ephedrine alkaloids, including ephedra, Ma huang, Sida cordifolia, and pinellia, because of potential complications. These supplements were aggressively marketed for weight control, as well as for energy and sports performance. Although they may effect modest short-term weight loss, these drugs raise blood pressure, stress the circulatory system, and have been linked to heart attack and stroke.