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Weight-loss drugs: Alli and Xenical (Orlistat)

Slim benefits and embarrassing side effects

Last updated: August 2009

The Big Loser: Risks appear greater than the benefit.

A review of several thousand adverse event reports from the Food and Drug Administration associated with orlistat—the active ingredient in the over-the-counter (OTC) weight-loss drug Alli and the prescription drug Xenical--has further strengthened our earlier advice: Skip this drug.

The reports, obtained through a Freedom of Information Act request we filed with the FDA earlier this year, show a pattern of adverse events submitted to the agency since Jan. 1, 2007, including rectal bleeding and kidney, liver and thyroid problems. Those reports don't prove that orlistat is to blame; but only that those conditions are associated in the reports with the use of Alli and Xenical. To date, a clear link between the use of the drug and a majority of those side effects has not been firmly established. The FDA is already investigating liver toxicity issues associated with both drugs, and with rectal bleeding with Xenical.

Of the several thousand reports submitted to the FDA, Charles Bennett, director of the Research on Adverse Drug Events and Reports (RADAR) group, which also reviewed the reports said "this safety concern is heightened when one considers that only an estimated 1 percent to 10 percent of all adverse events that occur are ever reported to the FDA."

Risks and benefits

Indication and risks. Orlistat is a powerful medication meant for people who are overweight or obese. Both Alli and Xenical are specifically approved to be taken only while also adhering to a low-calorie diet and exercise program. The OTC version, Alli, contains half as much as orlistat as doctor-prescribed Xenical does.

Orlistat works by blocking enzymes in the gut that normally digest fat, thus preventing its absorption. (During our review of the latest information one of our medical consultants commented that "fat malabsorption," as the condition is known, is actually a disease.) But that lack of absorption can lead to a number of adverse effects.  In clinical trials of Xenical, during the first year of use, 27 percent of people experienced oily underwear staining, 24 percent had gas with involuntary discharge of stool, 22 percent experienced fecal urgency, 11 percent had an increased number of bowel movements, and 8 percent suffered fecal incontinence. Virtually everyone who takes orlistat experiences diarrhea, at least, occasionally.

Most people can reduce the frequency and severity of those unpleasant side effects by cutting the amount of fat in their diets to 30 percent or less. But even then they must make other nutritional adjustments, since orlistat also hinders the absorption of fat-soluble vitamins, notably beta-carotene (vitamin A), vitamin D, vitamin E, and vitamin K.

In addition, the prescription version (Xenical) includes warnings on its label about the possibility of pancreatitis (inflammation of the pancreas).


The benefits. Even when orlistat is combined with exercise and nutritional changes, it produces only a modest 5 percent to 10 percent decline in body weight. Three studies done before the approval of orlistat measured weight loss over a one-year period in obese patients with and without type 2 diabetes. They had a BMI (body mass index) over 28 and were on a reduced-calorie diet. At the beginning of the trials, the patients weighed an average of 220 pounds. Pooled data show that the average weight loss with orlistat was about 19 pounds vs. 12 pounds with a placebo. Other trials found similar evidence of limited effectiveness.
But the most important question is: Does the evidence show that orlistat reduces premature death and disability? The answer is no. Even the manufacturer notes this in Xenical's drug labeling. A systematic review of the evidence published in the British Medical Journal on orlistat and two other weight loss drugs also found there was no evidence that it reduces death or the risk of cardiovascular disease.

It's true: Americans are getting fatter. The percentage of obese people in the U.S. has doubled—from 15 percent to 32 percent—in the last two decades. To stave off those unwanted pounds, consumers spend billions of dollars a year on weight loss products. While it is clear that weight loss in general can improve health, according to Consumer Reports medical advisors, orlistat is not the answer.


The bottom line. The risks of orlistat vastly outweigh the benefits. The millions of Americans who legitimately need to lose weight are far better off avoiding orlistat and weight-loss gimmicks. They should focus instead on what has been shown to work, without the risks: engaging in regular exercise, eating fewer calories, and sticking with both.

This drug safety alert is made possible through a partnership between Consumer Reports Best Buy Drugs and The Research on Adverse Drug Events and Reports (RADAR) group, a pharmacovigilance group led by Charles Bennett, MD PhD MPP. This is the second in a series of reports based on research by the RADAR group.

These materials are made possible by a grant from the state Attorney General Consumer and Prescriber Education Grant Program, which is funded by the multi-state settlement of consumer fraud claims regarding the marketing of the prescription drug Neurontin (gabapentin).

If you think you have experienced an adverse event with this drug or any drug, especially if it is of a serious nature, it is important to 1) tell your doctor immediately and 2) report the event to the Food and Drug Administration via the FDA's MedWatch website at https://www.accessdata.fda.gov/scripts/medwatch/medwatch-online.htm or by calling 1-800-FDA-1088.
   

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