Orlistat is a drug designed to treat obesity. It is marketed as a prescription drug under the trade name Xenical by Roche in most countries, and is sold over-the-counter as Alli by GlaxoSmithKline in the United Kingdom and the United States. Its primary function is preventing the absorption of fats from the human diet by acting as a lipase inhibitor, thereby reducing caloric intake. It is intended for use in conjunction with a healthcare provider-supervised reduced-calorie diet.
Orlistat is the saturated derivative of lipstatin, a potent natural inhibitor of pancreatic lipases isolated from the bacterium Streptomyces toxytricini. However, due to its relative simplicity and stability, orlistat was chosen over lipstatin for development as an anti-obesity drug.
The effectiveness of orlistat in promoting weight loss is definite but modest. Pooled data from clinical trials suggest that people given orlistat in addition to lifestyle modifications, such as diet and exercise, lose about 2–3 kilograms (4.4–6.6 lb) more than those not taking the drug over the course of a year. Orlistat also modestly reduces blood pressure and appears to prevent the onset of type 2 diabetes, whether from the weight loss itself or other effects. It reduces the incidence of diabetes type II in people who are obese around the same amount that lifestyle changes do.
How to use Xenical
If you are taking the over-the-counter product to self-treat, read all directions on the product package before taking this medication.
If your doctor has prescribed this medication, read the Patient Information Leaflet if available from your pharmacist before you start taking orlistat and each time you get a refill. Take this medication as directed by your doctor, by mouth with liquid sometime during each meal that contains fat or within 1 hour after the meal, usually 3 times daily. If you miss a meal or your meal contains no fat, skip that dose of the medication. To decrease the chance of unpleasant side effects, it is very important that no more than 30% of the calories in your diet come from fat. Your daily intake of fat, protein, and carbohydrates should be evenly spread over 3 main meals.
Do not increase your dose or use this drug more often or for longer than prescribed. Your condition will not improve any faster, and your risk of side effects will increase.
Because this drug can interfere with the absorption of certain vitamins (fat-soluble vitamins including A, D, E, K), a daily multivitamin supplement containing these nutrients is recommended. Take the multivitamin at least 2 hours before or 2 hours after taking orlistat (such as at bedtime).
If you take cyclosporine, take it at least 3 hours before or after orlistat to make sure the full dose of cyclosporine is absorbed into your bloodstream. If you take levothyroxine, take it at least 4 hours before or after orlistat.
You should see some weight loss within 2 weeks after you start orlistat. Tell your doctor if your condition does not improve or if it worsens.