The Food and Drug Administration has approved orlistat (Xenical: Roche), a new drug to treat obesity. Orlistat is the first drug in a new class of non-systemically acting anti-obesity drugs know as lipase inhibitors.

Unlike other obesity drugs, orlistat prevents enzymes in the gastrointestinal tract from breaking down dietary fats into smaller molecules that can be absorbed by the body. Absorption of fat is decreased by about 30%. Since undigested triglycerides are not absorbed, the reduced caloric intake may have a positive effect on weight control.

The recommended dose of orlistat is 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% of calories from fat. Orlistat is indicated for obese patients with a body mass index (BMI, a measure of weight in relation to height), of 30 or more, or for patients with a BMI of 27 or more who also have high blood pressure, high cholesterol, or diabetes. A person who is 1.60 metres in height and weighs 180 pounds would have a BMI of 30.

Because orlistat reduces the absorption of some fat-soluble vitamins and beta carotene, patients should take a supplement that contains these fat-soluble vitamins (A, D, E, and K) and beta carotene. The most common adverse effects of orlistat are oily spotting, gas with discharge, fecal urgency, fatty/oily stools and frequent bowel movements.

Reference: FDA Talk Paper T99-19 dated 26 April 1999.