<p>Orlistat is a potent, specific and long-acting lipase inhibitor. It exerts its therapeutic activity in the lumen of the stomach and upper small intestine by forming a covalent bond with the active serine site of gastric and pancreatic lipases. The inactivated enzyme is thus rendered unable to hydrolyze dietary fats in the form of triglycerides into absorbable free fatty acids and monoglycerides. As undigested triglycerides can not be absorbed, a caloric deficit arises which has a positive effect on weight control. Systemic absorption of orlistat is therefore not needed for the activity. At the recommended therapeutic dose of 120 mg three times a day, orlistat inhibit dietary fat absorption by approximately 30%.</p>