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Orlistat (marketed as Xenical by Roche) is a drug designed to treat obesity. It works by inhibiting pancreatic lipase, an enzyme that breaks down fat in the intestine. Without this enzyme, fat from the diet is excreted undigested, and not absorbed by the body. more...


Orlistat is available on prescription, although, as with many prescription drugs, it is possible to obtain it from online pharmacies. In 2004, a lower-dose version of the drug (60 mg compared to 120 mg for the prescription dose) was released over the counter in Australia and New Zealand; the United States is expected to follow in the near future.

It has a number of side effects related to digestion. Because its main effect is to prevent dietary fat from being absorbed from the gut, the fat is excreted and so the stool becomes oily, runny, and gassy. Bowel movements may become frequent, urgent or uncontrollable. To minimize these effects, the fat content of the diet should be reduced to about 30%. Obviously many patients find these side effects uncomfortable, and this has resulted in serious compliance issues.

The drug should only be taken when there is fat in a meal (it will not work if there is no fat in the diet). Because some vitamins are fat soluble, the effect of Orlistat is to reduce their absorption. A multivitamin tablet containing these vitamins (D E K and beta-carotene) should be taken once a day, at least 2 hours before or after taking the drug.

The amount of weight loss achieved with Orlistat is quite modest. The weight loss in a 4-year double-blind trial averaged only 2.8 kilograms (about 6 pounds) more than placebo. Despite this cosmetically small effect, there was a 37% reduction in the incidence of diabetes, a medically very significant difference.

You must not take Xenical if you:

  • have problems absorbing food
  • have reduced gallbladder function
  • are pregnant, or are still breast-feeding (it is not known whether Xenical is expressed in breast milk)
  • have certain kidney problems (consult your doctor).


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Two weight loss drugs—Meridia and Xenical the pros and cons of each
From Healthfacts, 2/1/04

Thinking of taking a weight loss drug? Now that the popular dietary supplement ephedra has been linked to sudden cardiac death and is due to be removed from the market by the Food and Drug Administration, more people may turn to one of the two widely promoted prescription drugs for weight loss: Meridia and Xenical. Both are oral drugs that can produce modest weight loss in adults when used with a restricted calorie diet. Here are some of the pros and cons of each drug.

MERIDIA (generic name: sibutramine)

Introduced in 1998

Supporting Research: Altogether 11 clinical trials have been conducted in which obese and overweight people went on a reduced calorie diet and were randomly assigned to take Meridia or a placebo. The trials lasted for 12 to 52 weeks. After one year, participants taking 10 mg a day of Meridia lost ten pounds, and those taking 15 mg of Meridia lost 14 pounds. The people solely on the reduced calorie diet lost 3 1/2 pounds. Weight was regained after Meridia was discontinued.

How it works: Meridia acts somewhat like an antidepressant. It decreases the appetite by blocking reuptake of nerve transmitters (norepinephrine, serotonin and dopamine) in brain synapses.

Downside: Meridia causes small increases blood pressure (1 to 3 mm Hg) with increases in pulse rate of four to five beats per minute. Side effects that may occur include headache, constipation, back pain, insomnia, drug mouth, nervousness and too many more to list. For a fuller description, read the drug label (see For More Information).

Caution: Use in people over age 60 requires careful consideration, as they are more likely to have high blood pressure and heart disease.

Cost: Approximately $3.83 a day, depending on where the drug is purchased.

XENICAL (orlistat) Introduced in 1999.

Supporting Research: The FDA has approved Xenical not only for weight loss but also for weight maintenance following weight loss. Altogether five clinical trials have been conducted in which 3,379 obese and overweight people went on a reduced calorie diet and were randomly assigned to take Xenical or a placebo. The amount of weight loss at one year was similar to that of Meridia. After one year of treatment, three trials looked at the percentage of people who regained weight. People who had been on the placebo regained 52% of the weight lost during the clinical trials, and people who had been on Meridia regained 26% of the weight lost while on the drug.

How it works: It works in the intestines, where it blocks some of the fat a person eats from being absorbed and digested. This undigested fat is eliminated in the person's bowel movements (BMs).

Downside: Gastrointestinal distress: The most common side effects are changes in BMs, according to the drug label, including "oily, spotting BMs, gas with discharge, urgent need to have a BM, oily or fatty stools, an oily discharge, fecal incontinence," etc. The rate of these adverse reactions rises according to increases in dietary fat intake. Xenical blocks the body's uptake of fat-soluble vitamins, making supplementation necessary.

Caution: Safety in people over the age of 60 is unknown. They were not represented in the clinical trials.

Cost: Approximately $3.56 a day, depending on where the drug is purchased.

For More Information.

Both the physician and patient labeling information can be read in the Physicians' Desk Reference, available at public libraries, and on the FDA web site (, go to "drugs", "drug approval," name of drug, and click into the date in the right-hand column entitled "label posted," or call 1(888) 463-6332.

COPYRIGHT 2004 Center for Medical Consumers, Inc.
COPYRIGHT 2004 Gale Group

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