Orlistat is a lipase inhibitor: it blocks the gut enzymes that break down fat, so less fat from a meal is absorbed; the label says about 30% less at the 120 mg dose. It works in the gut and very little enters the blood. It is sold by prescription as Xenical (120 mg); a lower-strength orlistat product is sold over the counter as Alli. This page uses the Xenical label.
Also known as: Xenical, Alli.
Xenical comes as a 120 mg capsule.
The Xenical label approves orlistat for obesity management, including weight loss and keeping it off, with a reduced-calorie diet, and to lower the risk of regain after weight loss, in people with a starting BMI of 30 or more, or 27 or more with risk factors such as high blood pressure, diabetes or high blood fats. Label dosing: one 120 mg capsule three times a day with each main meal that contains fat, during the meal or up to 1 hour after; if a meal is skipped or has no fat, that dose can be left out. Doses above 120 mg three times a day added no benefit. The label pairs it with a balanced diet with about 30% of calories from fat, and a daily multivitamin with vitamins A, D, E, K and beta-carotene taken at least 2 hours apart, such as at bedtime.
The label has no boxed warning. It is not used in pregnancy, with chronic malabsorption, or with cholestasis (blocked bile flow). Warnings cover lower vitamin absorption and interactions with cyclosporine, levothyroxine, warfarin, amiodarone, seizure medicines and HIV medicines; rare severe liver injury; oxalate kidney stones; and gallstones. Most side effects come from unabsorbed fat: oily spotting (26.6% vs 1.3% on placebo), gas with discharge (23.9% vs 1.4%), urgent bowel movements (22.1% vs 6.7%) and fecal incontinence (7.7% vs 0.9%), usually in the first 3 months. See Xenical side effects, Xenical dosing schedule, missed Xenical dose, Xenical vs Qsymia and Xenical vs Wegovy.
The Xenical label says very little orlistat is absorbed: after a 360 mg radio-labeled dose, intact orlistat in the blood was near the limit of detection, and in treatment studies it was found only now and then at low levels, so we do not list a half-life or time to peak for orlistat itself. Most of the dose leaves unabsorbed in the stool. Its two weak breakdown products had half-lives of about 3 hours and 13.5 hours.
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