The Cleveland Clinic

Weight Loss:
Prescription Weight Loss Medicine

Obesity 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 people. While most side effects of prescription medications for obesity are mild, serious complications have been reported (see below.)

Keep in mind that these drugs are not a cure-all. The use of weight-loss medications should be combined with physical activity and improved diet to lose and maintain weight successfully over the long term .

Do I Need Medicine to Lose Weight?

Using prescription drugs to treat obesity should be used as an option for the following individuals:

  • People with a body mass index (BMI) > 30 with no obesity-related conditions.
  • A person with a BMI of > 27 with two or more obesity-related conditions .

What Prescription Medicines Are Used to Treat Obesity?

Currently, most available weight-loss medications approved by the FDA are for short-term use, meaning a few weeks or months.

Most available weight-loss medications are "appetite-suppressant" medications. These include: Didrex, Tenuate, Sanorex, Mazanor, Adipex-P and Meridia. These medications generally come in the form of tablets or extended-release capsules (pills that release medication over a long period of time). Appetite suppressants can be obtained by a doctor's prescription or purchased over the counter .

In the mid 1990s doctors also prescribed the popular appetite suppressant Redux or the combination of phentermine and fenfluramine, called "Phen-fen." However fenfluramine (Pondimin) and Redux were withdrawn from the market in 1997 because they caused damage to heart valves. Phentermine is still available. Taking phentermine alone has not been associated with the adverse health effects of the fenfluramine-phentermine combination.

Another type of prescription weight loss drug is a fat absorption inhibitor. Xenical is the only example of this type of treatment approved for use in the U.S. Xenical works by blocking about 30% of dietary fat from being absorbed, and is the most recently approved weight loss drug.

Meridia and Xenical are the only weight-loss medications approved for longer-term use in significantly obese people, although the safety and effectiveness have not been established for use beyond 1 year.

How Do Appetite Suppressants Work?

Appetite suppressants promote weight loss by tricking the body into believing that it is not hungry or that it is full. They decrease appetite by increasing serotonin or catecholamine -- two brain chemicals that affect mood and appetite.

How Do Fat Absorption Inhibitors Work?

Fat-absorption inhibitors work by preventing your body from breaking down and absorbing fat eaten with your meals. This unabsorbed fat is eliminated in bowel movements.

Do Prescription Weight Loss Drugs Really Work?

In general, Xenical and Meridia are moderately effective, leading to an average weight loss of 5 to 22 pounds over a 1 year period, more than what would be expected with non-drug treatments. However, the response to these medications is based on each individual, and some people experience more weight loss than others. Likewise, there is no one correct dose for these medications. Your doctor will decide what works best for you based on his or her evaluation of your medical condition and your response to treatment.

Some people have lost more than 10% of their initial body weight with the help of prescription medications. This is a large enough amount to reduce the risk of high blood pressure, diabetes and other obesity-related health complications . Patients generally experience a maximum weight loss within 6 months of starting medication treatment.

Over the short term, weight loss due to prescription drugs may reduce a number of health risks in obese individuals. However, there are currently no studies to determine the effects of these medications over the long term.