Weight Loss Medications: Obesity

Content provided by the Faculty of the Harvard Medical School

Weight-loss medications

Diet drugs have gotten a lot of press. In June of 2007, an over-the counter version of the fat-blocking drug orlistat (Xenical) hit drug store shelves. Dubbed Alli, the drug works by blocking fat absorption in the intestines and must be taken before every fat-containing meal. Many physicians and patients were enthusiastic about rimonabant (Acomplia), a drug that works by blocking the same receptors in the brain that cause the "munchies" in marijuana users. Rimonabant is currently available in many European countries. But in 2007, a federal advisory committee recommended against the drug's approval in the US, citing concerns that rimonabant may leave people vulnerable to neurological and psychiatric problems—including a higher risk of suicide.

Other currently available prescription weight-loss drugs include those that suppress or regulate appetite by altering levels of brain chemicals — namely, sibutramine (Meridia) and phentermine (Adipex, Ionamin, others).

Of course, weight-loss drugs don't do the job by themselves. But for people whose health is at risk and who are struggling to reduce their weight through diet and exercise, drug therapy may increase the odds of success. Experts agree that weight-loss drugs, which all have side effects, are not for the mildly overweight or those who just want to lose a few pounds to improve their appearance.

Researchers have learned a lot about the biological causes of weight disorders, such as how genes influence the many systems that control weight. Weight-loss drugs can temporarily manipulate these systems. More than 200 drugs currently are in the testing phase.

Weight medications have a history of safety concerns. In the 1950s and 1960s, dieters took amphetamines to quell their appetites and boost their metabolisms — until it was discovered that the pills were addictive and caused paranoia. The combination of fenfluramine and phentermine, popularly known as fen-phen, was widely used in the mid-1990s, until fenfluramine and another drug, dexfenfluramine, were linked to heart valve disease and withdrawn from the market. (Phentermine, the weaker but safe half of fen-phen, is still used.)

Until sibutramine was approved in 1997 for long-term use in obesity, the FDA had required that most such medications be prescribed for no longer than three months. Both sibutramine and orlistat are approved for use up to one year, but physicians may prescribe them for longer. Sibutramine is considered effective and safe for up to two years, although it can increase blood pressure and thus requires monitoring. Orlistat, which inhibits the body's ability to absorb fats, can interfere with the absorption of fat-soluble vitamins. Moreover, little is known about how safe it is to use weight-loss drugs for more than two years.

On the other hand, these medications have a role to play in medical treatment, especially now that obesity is recognized as a metabolic disease and not a failure of motivation or willpower, as was once thought. Clinicians are finding that obesity, like other chronic conditions, is often easier to manage with judicious, long-term medication use.

Last updated:	June 20, 2007