Weight-loss medications

Several prescription weight-loss drugs are available. Ask your health care provider if any of these are right for you.

People lose 5 - 10 pounds by taking these drugs, but not everyone loses weight while taking them. Most people also regain the weight when they stop taking them, unless they have made lasting lifestyle changes, such as exercising and cutting unhealthy foods from their diet.

You may also see ads for supplements that claim they will help you lose weight. But many of these claims are not true, and some of these supplements have serious side effects.

See also: Herbal remedies and supplements for weight loss

A special note for women: Pregnant or nursing women should never take diet medicines of any kind. This includes prescription, herbal, and other over-the-counter remedies. Over-the-counter refers to drugs or supplements you can buy without a prescription.

Weight-loss Drugs

Note: Sibutramine (Meridia) has been taken off the market because of concern for serious side-effects.

Orlistat (Xenical and Alli)

People can lose about 6 pounds when they use this drug, but not everyone loses weight while taking it. Many people regain most of this weight within 2 years after stopping the drug.

The most unpleasant side effect of orlistat is oily diarrhea, which may leak from the anus. Eating fewer fats can reduce this effect. Even with these side effects, most patients are able to tolerate this medicine.

Xenical is the form of this drug your health care provider can prescribe for you. You can also buy orlistat without a prescription under the name Alli. These pills are half the strength of Xenical. They will cost about $100 a month. Consider whether the cost, side effect of oily diarrhea, and the small weight loss you can expect are worth it to you.

Your body may not absorb important vitamins, minerals, and other nutrients from food while you are using orlistat. You should take a daily multivitamin supplement if you take this drug.

Phentermine, Benzphetamine, and Phendimetrazine

These drugs stimulate your brain. This means they will make you more alert and wakeful. They also make you less interested in food.

Some of these stimulants are approved for treating obesity. The average weight loss while taking these drugs is about 5.8 pounds, but not everyone loses weight while taking them. Most people regain the weight when they stop taking the drug, unless they have made lasting lifestyle changes.

Some brand names of each of these drugs are:

  • Phentermine (Ionamin, Adipex-P, Fastin)
  • Benzphetamine (Didrex)
  • Phendimetrazine (Adipost, Bontril, Melfiat, Plegine, Prelu-2, and Statobex)
  • Diethylpropion (Tenuate)
  • Phentermine is the most commonly prescribed of these drugs. It costs less than orlistat, but like orlistat, its effects do not last long.

Some side effects of phentermine are:

  • An increase in blood pressure
  • Problems sleeping, nervousness, palpitations, dry mouth, and constipation
  • Depression, which many people who are obese struggle with already

Note: Current drugs are NOT linked to the heart problems caused by the previous drug called Fen-Phen that contained phentermine.

(Note: You may want to ask your doctor about other weight-loss medications not discussed in this article. These include: exenatide ( Byetta), liraglutide (Victoza), naltrexone (Naltratone), topiramate, and zonisamide)

Update Date: 7/1/2011

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.


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