alli (pronounced AL-EYE) is a half-dose version of prescription Xenical^® (orlistat), and is the first weight-loss drug ever approved by the U.S. FDA for over-the-counter sale.

alli was scheduled to go on sale in the United States in mid-June 2007.

Orlistat, approved by the FDA in 1999, is a lipase inhibitor for obesity management that acts by inhibiting the absorption of dietary fats. Xenical prevents enzymes in the gastrointestinal tract from breaking down dietary fats into smaller molecules that can be absorbed by the body.

This undigested fat is removed in your bowel movements, and absorption of fat is decreased by about 30 percent.

Like Xenical, the recommended dose of alli will be one capsule with each main meal that includes fat. During treatment, the patient should be on a nutritionally balanced, reduced-calorie diet that contains no more than 30 percent of calories from fat.

The most common side effects of Xenical are oily spotting, gas with discharge, fecal urgency, fatty/oily stools and frequent bowel movements.