orlistat is used with a low-calorie diet to help you lose weight and to maintain your weight after weight loss. orlistat is used in patients with a certain weight who may also have high blood pressure, diabetes, high cholesterol, or heart disease. mechanism: orlistat is in a class of drugs called lipase inhibitors. it works in your intestines, where it blocks some of the fat you eat from being absorbed and disgested. this undigested fat is then removed in your bowel movements (bm). dosage and usage: each time you take orlistat, your meal should contain no more than about 30% of calories from fat. take orlistat during or up to 1 hour after a meal. if a meal is missed or does not have fat, you may skip your dose. follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. take orlistat exactly as directed side effect: the most common side effect of orlistat is changes in bowel movement (bm) habits. this generally occurs during the first weeks of treatment; however, it may continue throughout your use of orlistat. tell your doctor if any of these symptoms are severe or do not go away: • oily, spotting bms • gas with discharge • urgent need to have a bm • oily or fatty stools • an oily discharge • increased number of bms • inability to control bms • orange or brown color of a bm • stomach pain • irregular menstrual periods storage: store it at room temperature and away from excess heat and moisture.