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Weight-loss Drugs

Prescription Drug Therapies

For people who've tried everything else to control their weight without success, prescription weight-loss drugs may help. If you've already tried eating less, exercising more, and joining a weight loss program for at least six months, and none of these has helped, you might be a candidate for a weight-loss drug.

"Prescription weight-loss drugs are only given to patients who have made an effort to lose weight without drugs," says Richard A. Dickey, M.D. "We use drugs as an option after other, safer means of weight loss haven't worked."

Even with this precaution, weight-loss drugs have had some bad publicity, thanks largely to the "fen-phen" case in late 1997. The Food and Drug Administration withdrew its approval of this combination because the two medications involved, fenfluramine and phentermine, caused serious heart valve problems in some people. The decision attracted much attention from the media, and since then, people have been understandably cautious about prescription weight-loss drugs. But some drugs are relatively safe for shedding pounds and maintaining weight loss when used under an experienced physician's care.

Before you consider asking your physician about prescription weight-loss drugs, do some research. Be aware of who should and shouldn't take these drugs, what's available, how they work, how well they work, what their side effects are, and what they cost.

Who should take them?

These drugs are for people who are obese — that is, for someone who has a body mass index of 30 or more, or a BMI of 27 or more plus at least one health risk factor related to obesity. Risk factors include diabetes, high cholesterol, and high blood pressure.

If you're 5'4", for example, you might be a candidate for prescription drugs (assuming you've tried other weight-loss methods first) if you weigh over 174 pounds, or if you weigh between 157 and 174 and have high blood pressure. (Use the BMI calculator to measure your own body mass index).

These drugs aren't for people who are trying to lose just five or 10 pounds. And they aren't safe if you are pregnant or nursing, or if you have an unstable heart condition or uncontrolled high blood pressure. They're also not safe if you're taking other drugs that might be harmful in combination with them — especially the MAO inhibitors, antidepressants such as Nardil, Parnate, and Marplan, other weight-loss drugs, and some over-the-counter cough, cold, decongestant, and allergy medications. They shouldn't be used for the specific purpose of weight loss if you're taking any of the SSRI antidepressants (Prozac, Paxil, Zoloft, and Celexa). Always let your doctor know what medications you are taking.

What's out there?

About 14 prescription weight-loss drugs are available. Two of these, orlistat (brand name Xenical) and sibutramine (Meridia), are approved for long-term use (up to one year). Other weight-loss drugs are prescribed only for short-term use (no more than three months); some of these are phentermine (brand names include Adipex-P, Obe-Nix 30, and Ionamin), mazindol (Sanorex), and diethylpropion (Tenuate and Tenuate Dospan).

How do they work?

These drugs can help, but they aren't magic. Your physician will be quick to remind you that just taking a drug isn't enough. "To be successful at losing weight," says Dickey, "you have to make behavioral changes. You have to restrict your calorie intake and increase your physical activity." According to Dickey, prescription weight-loss pills can make it easier for you to start those changes and maintain them.

Prescription weight-loss drugs generally work in your body in one of two ways. Most of them — including Meridia and most of the short-term drugs — work on the neurotransmitters in your brain that regulate appetite. Simply put, these drugs help your body feel satisfied on less food. On the other hand, Xenical, works on a different premise. It blocks your body's absorption of fat from foods you've eaten.

Approved for up to one-year use

Drugs that have been approved for long-term use have passed rigorous testing that shows they are safe to use for up to a year. They help you not only lose weight but maintain your new weight as well.

  • Xenical is the drug available for weight loss, approved by the FDA in April 1999. The drug keeps fat-busting enzymes in the small intestine from doing their work, with the result that about one-third less fat is absorbed into the body. Instead, your body gets rid of the undigested fat by excreting it in stools.
  • Meridia, approved by the FDA in November 1997, works in a completely different way. Meridia (sibutramine) was withdrawn from the U.S. market in October 2010. This drug "signals" your brain that you are full so that you eat less. Meridia acts on your brain's neurotransmitters, affecting levels of norepinephrine, serotonin, and dopamine, chemicals that cause you to feel satisfied when you've had enough food — your stomach's fullness gauge.

Approved for short-term use

Short-term drugs should be used no longer than three months. Your body is more likely to build up a tolerance to one of these drugs, making it ineffective. But you may be able to use short-term drugs three months on and three months off for more than a year with good results.

  • Phentermine is the "phen" part of fen-phen. On its own, it rarely leads to the heart problems associated with the fen-phen combination. Phentermine reduces hunger by working on the hypothalamus, the part of the brain that controls appetite.
  • Mazindol (Sanorex) affects how certain neurotransmitters absorb norepinephrine and dopamine, chemicals that signal the brain that the stomach is full.
  • Like phentermine, diethylpropion acts on the hypothalamus, the brain's appetite center, to lessen hunger.

How successful are they?

Prescription weight-loss drugs have been tested primarily on people who meet official guidelines for obesity — that is, a BMI of 30 or more. Such people who eat less, exercise, and take prescription weight-loss drugs are more likely to lose weight than people who just eat less and exercise. These drugs also seem to help them maintain their lower weight over time, as long as the medications are taken as prescribed and lifestyle changes are continued. Overall, the effect on weight loss from these drugs is modest, averaging five to 12 pounds after one year.

Some people who take prescription weight-loss drugs lose up to 10% of their original weight. That may not sound like much, but it may be enough to kick-start them on the road to greater weight loss. On the other hand, weight loss with the help of prescription drugs usually reaches a plateau after six to eight months, and the drug may have to be continued to maintain the weight loss. Also, about one-third of those who take weight-loss drugs don't respond to them and don't lose weight.

What are the drugs' side effects?

In general, weight-loss drugs that work on the brain's neurotransmitters, such as Meridia and the short-term drugs (phentermine, mazindol, and diethylpropion), have similar side effects, including dry mouth, constipation, restlessness, insomnia, headache, and nervousness. These drugs can also increase blood pressure and heart rate, and shouldn't be combined — for example, Meridia and phentermine should never be taken together. Note that weight-loss drugs have only been approved for use individually; taking more than one during the same period could lead to severe side effects.

Because Xenical prevents absorption of some fats, those who take it may not be absorbing enough of the fat-soluble vitamins (A, D, E, and K) and beta-carotene. This can put you at risk for malnutrition if a physician isn't carefully supervising you. Be sure to take a multivitamin while on Xenical. You may also experience oily stools or more frequent bowel movements — especially if you indulge in a high-fat meal.

Avoid problems

Always tell your doctor about all medications you are taking.


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