Appetite-suppressant medications are drugs that promote weight loss by decreasing appetite or increasing the sensation of fullness.
Obesity is a disease that affects millions of American adults, adolescents, and children, posing serious health risks. Medical professionals generally consider obesity to be a chronic illness requiring life-long treatment and management. It is often grouped with other chronic conditions, such as high blood pressure and diabetes, as a condition that can be controlled but not cured. One is considered obese if 20% over ideal body weight, according to standard height-weight charts, or if one's Body Mass Index, or BMI, (a ratio of height to weight, indicaating the amount of fat tissue in the body) exceeds 30%.
The most important strategies for managing obesity are not medications but rather, a healthy diet coupled with moderate exercise. As in other chronic conditions, the use of prescription medications may assist in managing the condition for some individuals but it is never the sole treatment for obesity, nor is it ever considered a cure.
The class of medications used most often for weight loss are commonly referred to as "appetite suppressants." These medications promote weight loss by helping to diminish appetite, and/or by increasing the subjective feeling of fullness. They work by increasing serotonin or catecholamines, two neurotransmitters (chemicals) in the brain that affect both mood and appetite.
Several prescription medications are currently approved for treatment of obesity. In general, the effects of these medications are modest, leading to an average initial weight loss of between 5 and 22 pounds; though studies show that weight returns after cessation of the drugs. There is considerable individual difference in response to these medications; some people experience greater weight loss than others. The goal of prescribing weight loss medication is to help the medically at-risk obese patient "jump-start" their weight loss effort and lose 10% or more of their starting body weight. When this can be accomplished, it usually leads to a reduction in risk for obesity-related illnesses, such as high blood pressure, heart disease and diabetes. Weight loss tends to be greatest during the first few weeks or months of treatment, leveling off after about six months. Research suggests that if a patient does not lose at least four pounds during the first four weeks on a particular medication, that medication is unlikely to be effective over the long run. Few studies have addressed safety or effectiveness of medications taken for more than a few months at a time. Little data exists on the long-term effectiveness of the drugs.
All but two of the prescription appetite suppressants in the United States have been approved by the U.S. Food and Drug Administration (FDA), for short-term use only. Short-term use generally means a few weeks or months at the longest. One appetite suppressant medication was approved for longer-term use within the past decade, but that drug, dexfenfluramine (Redux) was withdrawn from the market because of unacceptable risks associated with its use.
Another medication was approved within the past few years for longer-term use, up to a year and possibly longer, in significantly obese patients. This drug, an appetite suppressant, is called sibutramine (Meridia). Individuals with a history of heart disease, irregular heartbeat, high blood pressure, or history of stroke should not take sibutramine. All patients taking this medication should have their blood pressure monitored regularly.
A relatively new drug, orlistat (Xenical), was approved in 1999 by the FDA for at least a year or longer, as well. Orlistat is not an appetite suppressant, but rather, a member of a new class of anti-obesity drugs known as "lipase inhibitors." These medications work by preventing enzymes in the gastrointestinal tract from breaking down dietary fats into smaller molecules that can be absorbed by the body. The result is that fat absorbed from food is decreased by about 30%. This effectively reduces the calories absorbed by the body by 30%, aiding in weight loss.
While the FDA regulates how a medication can be advertised or promoted by the manufacturer, these regulations do not constrain physicians from prescribing them as they believe appropriate. This practice of prescribing medications for conditions other than those for which they were approved, or at different dosages, or for different lengths of time, is known as "off-label" use. Many of the prescription medications available for weight management are used in an "off-label" manner.
Most of the side effects of prescription medications for weight loss are mild; but some very serious complications have been reported in recent years. They were so serious that two medications were voluntarily removed from the market by the manufacturers in 1997.These two medications, fenfluramine (Pondimin), and dexfenfluramine (Redux), were shown to be associated with a rare but very serious and potentially fatal disorder known as primary pulmonary hypertension (PPH), a disease of the lungs. Forty-five percent of patients with PPH die within four years of diagnosis .
Medications for weight loss
Prescription medications currently prescribed for weight loss include:
- Generic name: Diethylpropion (Trade names: Tenuate, Tenuate dospan)
- Generic name: Mazindole (Trade name: Sanorex)
- Generic name: Orlistat (Trade name: Xenical)
- Generic name: Phendimetrazine (Trade names: Bontril, Plegine, Prelu-2, X-Troxine)
- Generic name: Phentermine (Trade name: Adipex-P, Fastin, Ionamin, Oby-trim)
- Generic name: Sibutramine (Trade name: Meridia)
Some antidepressant medications have been studied for use as possible appetite depressants, because they frequently depress appetite in the early weeks and months of use. Research indicates, however, that while individuals may lose weight initially during antidepressant treatment, a tendency to lose only modest amounts of weight arises after six months. Furthermore, most patients who lose weight early in antidepressant medication treatment tend to regain the weight while still using the medication.
Amphetamines and similar medications were frequently prescribed in the United States, during the 1960s and 70s, as appetite suppressants. However, because of their addictive potential, they are not prescribed today for weight control, except by a remainder of "diet doctors" who defy political correctness and continue to distribute them.
SINGLE DRUG TREATMENT. The medications listed above are currently used to treat obesity. In general, these medications are modestly effective, especially when used in conjunction with a healthy diet and moderate exercise. Average weight losses between five and 22 pounds can be expected beyond those seen with non-drug obesity treatments, when only a low-calorie diet and exercise regimen are followed. There is considerable individual variation in response to weight-loss medications; some people experience more weight loss than others.
COMBINED DRUG TREATMENT. Combined drug treatment using fenfluramine and phentermine ("fen/phen") is no longer available due to the withdrawal of fenfluramine from the market. There is little information about the safety or effectiveness of other prescription drug combinations for weight loss. Until further research is conducted on safety or effectiveness, using combinations of medications for weight loss is not advised unless a patient is participating in a research study.
POTENTIAL BENEFITS OF APPETITE SUPPRESSANT TREATMENT. Short-term use of appetite suppressant medications has been shown to modestly reduce health risks for obese individuals. Studies have found that these medications can lower blood pressure, blood cholesterol, blood fats (triglycerides), and decrease insulin resistance (the body's ability to utilize blood sugar). Long-term studies need to be conducted to determine if weight loss assisted by appetite suppressant medications can improve health long-term.
POTENTIAL RISKS OF APPETITE SUPPRESSANT TREATMENT. All prescription medications used to treat obesity, with the exception of orlistat, are controlled substances. This means that doctors need to follow rigid guidelines when prescribing them. Although abuse and dependence are uncommon with non-amphetamine appetite suppressant medications, doctors need to exercise caution when prescribing them, especially for patients with a history of alcohol or drug abuse.
DEVELOPMENT OF TOLERANCE. Studies of appetite suppressant medications indicate that an individual's weight tends to level off after four to six months of treatment. While some patients and doctors may be concerned that this indicates growing tolerance to the medications, the leveling off may indicate that the medication has reached its limit of effectiveness. Current research is not clear regarding whether weight gained with continued medication is due to drug tolerance, or to reduced effectiveness of the medication over time.
SIDE EFFECTS. Because obesity is a condition affecting millions of Americans, many of whom are basically healthy, the side effects of using powerful medications such as appetite suppressants are of great concern. Most side effects of these medications are mild and diminish as treatment continues. Rarely, serious and even fatal outcomes have been reported. The FDA-approved appetite suppressant medications that affect serotonin (fenfluramine and dexfenfluramine) have been withdrawn from the market. Medications that affect catecholamine levels (such as phentermine, dietylpropion, and mazindol) may cause symptoms of sleeplessness, nervousness, and euphoria.
Primary pulmonary hypertension (PPH) is a rare but potentially fatal disease that affects the blood vessels in the lungs and causes death within four years in 45% of its victims. Patients who use the appetite suppressant medications that are prescribed for a use of three months are at increased risk of developing this condition if used longer. Estimates are that between 1 in 22,000 and 1 in 44,000 individuals will develop the disorder each year. While the risk of developing PPH is very small, doctors and patients should be aware of this potentially deadly complication when they consider the risks and benefits of using appetite suppressant medications for long-term treatment of obesity. Patients taking appetite suppressants should contact their doctors if they experience shortness of breath, chest pain, faintness, or swelling in the lower legs and ankles. The vast majority of cases of PPH related to appetite suppressant use have occurred in patients taking fenfluarmine or dexfenfluramine, either alone or in combination with each other or other drugs, such as phentermine. There have been only a few cases of PPH reported among patients taking phentermine alone, although the possibility that phentermine alone may be associated with PPH cannot be ruled out at this time.
Animal research has suggested that appetite suppressant medications affecting the neurotransmitter serotonin, such as fenfluramine and dexfenfluramine, can damage the central nervous system. These findings have not been reported in humans. Some patients have reported depression or memory loss when using appetite suppressant medications alone or in combination, but it is not known if these problems are actually caused by the medications or by other factors.
Over-the-counter appetite suppressants
In addition to the numerous prescription medications for weight loss, a few over-the-counter agents are marketed for weight loss. The most common, phenylpropanalomine, is an appetite suppressant that is distantly related to the amphetamines. Like the amphetamines, this drug has the side effect of increased blood pressure and heart rate, and thus should not be used by anyone with hypertension or heart disease. Other over-the-counter medications contain fiber or bulking agents, and presumably work by increasing the sensation of fullness. Some preparations contain the anesthetic benzocaine. This agent numbs the mouth and may make eating less appealing temporarily. No evidence exists that any of these medications is effective in producing significant weight loss.
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Barbara S. Sternberg, Ph.D.