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Nutrition & Weight Control



Brand Name: Xenical
Drug Class: Lipase inhibitor
Available in: Capsules
Available Without a Prescription? No
Available As a Generic? No

Side Effects

Serious: No serious side effects have yet been reported.

Common: Oily spotting, gas with discharge, fecal urgency, oily stool, anal leakage, increased defecation, fecal incontinence.

Less common: Abdominal pain or discomfort.

Principal Uses

To achieve weight loss and weight maintenance in the maintenance of obesity when used in conjunction with a reduced-calorie diet and appropriate physical activity. Orlistat is indicated for patients with an initial body mass index (BMI) of 30 or greater and in those with a BMI greater than 27 (see Special Concerns for information on BMI calculation) who also have other risk factors such as high blood pressure, high blood cholesterol, and diabetes.

How the Drug Works

Orlistat inhibits the activity of lipases, intestinal enzymes required for the digestion of dietary fats. Orlistat prevents the breakdown of a portion of ingested fat. The undigested fat cannot be absorb-ed and is excreted in the feces. Full doses of orlistat reduce the absorption of fat by about 30%.


120 mg (one capsule) 3 times a day at mealtime.

Onset of Effect

Within 24 to 48 hours.

Duration of Action

48 to 72 hours.

Dietary Advice

Take with liquid during or up to one hour after each main meal containing fat. Follow a balanced, reduced-calorie diet. The daily intake of fat (approximately N of the calories), carbohydrate, and protein should be spread out over the three meals. If a meal is missed or contains no fat, the dose of orlistat can be skipped. Because orlistat can also reduce the absorption of fat-soluble vitamins, a multivitamin supplement (containing vitamins A, D, and E and beta-carotene) should also be taken once a day at least two hours before or after ingesting orlistat.


Store in a tightly sealed container away from heat, moisture, and direct light.

If You Miss a Dose

If you miss a dose, take it if you remember within 1 hour of eating. However, if more than 1 hour has passed, skip the missed dose and return to your regular schedule. Do not double the next dose.

Stopping the Drug

The decision to stop taking the drug should be made in consultation with your physician.

Prolonged Use

The safety and effectiveness of orlistat have not been determined beyond 2 years of use.


Over 60: No specific studies have been done on older patients.

Driving and Hazardous Work: No special warnings.

Alcohol: No special precautions are necessary.

Pregnancy: Adequate human studies have not been done. Before taking orlistat, tell your doctor if you are pregnant or plan to become pregnant.

Breast Feeding: It is unknown whether orlistat passes into breast milk. However, do not take the drug while nursing. Consult your doctor for advice.

Infants and Children: Safety and effectiveness have not been established for children under age 18.

Special Concerns: A medical cause for obesity (such as hypothyroidism) should be ruled out before taking orlistat. Consult your doctor or a nutritionist for information on a nutritionally-balanced, reduced-calorie diet and an exercise program. The BMI can be calculated by dividing your weight in pounds by your height in inches squared, and then multiplying by 705.


Symptoms: No cases of overdose have been reported.

What to Do: An overdose with orlistat is unlikely. If someone takes a much larger dose than prescribed, call your doctor.

Drug Interactions

The following drugs may interact with orlistat. Consult your doctor for specific advice if you are taking: cyclosporine, statin (cholesterol-lowering) drugs, warfarin, another weight-loss medication (such as sibutramine or phentermine), or any other prescription or over-the-counter drugs.

Food Interactions

Orlistat reduces the absorption of fat-soluble vitamins A, D, E, and K and beta-carotene. Gastrointestinal side effects may increase following the consumption of high-fat foods or with a diet high in fat (more than 30% of the day’s total calories from fat).

Disease Interactions

This drug should not be used if you have chronic malabsorption or gallbladder problems. Consult your doctor if you have an eating disorder (anorexia or bulimia).

From The Johns Hopkins Consumer Guide to Drugs. You can order this book now on our secure server.


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Nutrition & Weight Control

The Nutrition & Weight Control White Paper from The Johns Hopkins White Papers series is an annual, in-depth report written by Hopkins physicians.

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