Orlistat is a reversible inhibitor of lipases. It exerts its therapeutic activity non-systemically in the lumen of the stomach and small intestine by forming a covalent bond with the active serine site of gastric and pancreatic lipases.

The inactivated enzymes are thus unavailable to hydrolyze dietary fat in the form of triglycerides into absorbable free-fatty acids and monoglycerides. As undigested triglycerides are not absorbed, the resulting caloric deficit has a positive effect on weight loss, maintenance and prevention of weight regain. Systemic absorption of the drug is therefore not needed for activity.

Xenical is appropriate for those individuals who are considerably overweight, 30 percent above their ideal weight or a body mass index of 30 or greater.

Xenical may also be appropriate for those individuals who are overweight, 20 percent above their ideal weight or a body mass index of 27 or greater, and also have significant risk factors such as high blood pressure, high cholesterol or diabetes.

Xenical is used to help obese people who fit certain weight and height requirements lose weight and maintain weight loss. Xenical works in your intestines, where it blocks some of the fat you eat from being absorbed.

This undigested fat is then eliminated in your bowel movements. Use Xenical together with a reduced-calorie diet. The weight management effects of Xenical continue only as long as you are taking it.