Prescription medications for the treatment of obesity

White Paper by: National Institutes of Health, Jan 15, 1996

Prescription Medications for the Treatment of Obesity

Obesity is a chronic disease that affects many people and often requires long-term treatment to promote and sustain weight loss. As in other chronic conditions, such as diabetes or high blood pressure, long-term use of prescription medications may be appropriate for some individuals. Most side effects of prescription medications for obesity are mild, but rarely, serious complications can occur. Research suggests that appetite suppressant medications, when combined with changes in diet and physical activity, can help some obese patients lose more weight than with nondrug therapies and maintain weight loss for at least 1 year. However, few studies have looked closely at the safety or effectiveness of appetite suppressant medications when used for longer periods of time. Appetite suppressant medications should be used only by patients who are at increased medical risk because of their obesity and should not be used for "cosmetic" weight loss.

Medications That Promote Weight Loss

The medications most often used in the management of obesity are commonly known as "appetite suppressant" medications. Appetite suppressant medications promote weight loss by decreasing appetite or increasing the feeling of being full. These medications decrease appetite by increasing serotonin or catecholamine--two brain chemicals that affect mood and appetite.

Most currently available appetite suppressant medications are approved by the U.S. Food and Drug Administration (FDA) for short- term use, meaning a few weeks or months. Dexfenfluramine is the only medication currently approved for longer-term use (up to 12 months) in significantly obese patients. (See table 1 for the generic and trade names of prescription appetite suppressant medications. ) While the FDA regulates how a medication can be advertised or promoted, these regulations do not restrict a doctor's ability to prescribe the medication for different conditions, in different doses, or for different lengths of time. The practice of prescribing medication for periods of time or for conditions not approved is known as "off-label" use. While such use often occurs in the treatment of many conditions, your doctor should tell you if he or she is using a medication or combination of medications in a manner that is not approved by the FDA. The use of more than one appetite suppressant medication at a time (combined drug treatment) is an example of an off-label use.

Single Drug Treatment

Several appetite suppressant medications are available to treat obesity. In general, these medications are modestly effective, leading to an average weight loss of 5 to 22 pounds above that expected with non-drug obesity treatments. People respond differently to appetite suppressant medications, and some people experience more weight loss than others. Some obese patients using medication lose more than 10 percent of their starting body weight--an amount of weight loss that may reduce risk factors for obesity-related diseases, such as high blood pressure or diabetes. Maximum weight loss usually occurs within 6 months of starting medication treatment. Weight then tends to level off or increase during the remainder of treatment. Studies suggest that if a patient does not lose at least 4 pounds over 4 weeks on a particular medication, then that medication is unlikely to help the patient achieve significant weight loss. Few studies have looked at how safe or effective these medications are when taken for more than 1 year.

Some antidepressant medications have been studied as appetite suppressant medications. While these medications are FDA approved for the treatment of depression, their use in weight loss is an "off-label" use. Studies of these medications generally have found that patients lost modest amounts of weight for up to 6 months. However, most studies have found that patients who lost weight while taking antidepressant medications tended to regain weight while they were still on the drug treatment. NOTE: Amphetamines and closely-related compounds are not recommended for use in the treatment of obesity due to their potential for abuse and dependence.

Combined Drug Treatment

While there are a number of appetite suppressant medications approved to treat obesity, two medications have been combined to increase their ability to promote and sustain weight loss--fenfluramine and phentermine. In 1992, researchers at the University of Rochester reported on a 3 1/2-year study that looked at the safety and effectiveness of combining fenfluramine and phentermine to treat obesity. The study's findings were as follows:

Patients using fenfluramine and phentermine lost weight for about 6 months. Weight then tended to level off or to increase during the remainder of treatment.

Less than half of the 121 patients who began in treatment completed the entire study.

Between the second and third years of the study, many, but not all, patients experienced some weight gain. At the end of the study, patients still on the appetite suppressant medications had lost an average of about 15 pounds from their starting weights.