GENERIC NAME: orlistat

BRAND NAME: Xenical

DRUG CLASS AND MECHANISM: Orlistat is a drug that promotes loss of weight by preventing the digestion and absorption of dietary fat. In the intestine, an enzyme called lipase (produced primarily by the pancreas) breaks apart dietary fat so that the fat can be absorbed into the body. Orlistat blocks the action of lipase and thereby prevents the breakup and absorption of fat. The unabsorbed fat is excreted in the stool. Orlistat was approved by the FDA in 1999.

PRESCRIPTION: yes

GENERIC AVAILABLE: no

PREPARATIONS: Capsules:120 mg

STORAGE: Store tablets and capsules at room temperature, 15-30°C (59-86°F)

PRESCRIBED FOR: Orlistat is combined with a reduced-calorie diet to promote weight loss. Orlistat also may be used to prevent weight gain after weight has been lost. Candidates for treatment with orlistat are patients who are obese with a body mass index (a measure of obesity) of more than 30 kg/m2. Candidates also include patients with a body mass index of between 27 and 30 kg/m2 if other risk factors for arteriosclerosis are present such as high blood pressure, diabetes, and elevated blood cholesterol or triglycerides.

Based on several scientific studies, the average weight loss that is achieved when orlistat is taken as recommended for 6 months to one year is 12.4 to 13.4 pounds.

DOSING: The recommended dose for orlistat is one capsule (120 mg) three times daily. Orlistat should be taken one hour after or during a meal containing fat. Meals without fat do not require orlistat. No additional benefit has been shown when orlistat was taken in doses greater than 120mg. Patients should eat a nutritionally balanced, reduced calorie diet that contains approximately 30% of calories from fat.

Some dietary vitamins bind to fat (vitamins A, D, E and beta- carotene). When orlistat is taken, these vitamins are not absorbed and are eliminated in the stool in increased amounts along with the fat. Therefore, patients taking orlistat should take a multivitamin containing these "fat-soluble" vitamins to ensure that adequate amounts of the vitamins are available for absorption. To ensure that the vitamins in the multivitamins are not bound to fat like the vitamins in the diet, the multivitamin should be taken at least two hours before or several hours after the orlistat.

DRUG INTERACTIONS: The blood thinning effect of warfarin (Coumadin) depends on the amount of vitamin K in the body, and vitamin K is one of the vitamins that binds to fat. Patients receiving warfarin who begin orlistat should have their blood clotting monitored closely because the orlistat may cause levels of vitamin K to decline. This will increase the effects of warfarin and lead to abnormal bleeding from the warfarin. There is no evidence that a deficiency of vitamin K occurs in patients who are taking orlistat. Orlistat may reduce the absorption and blood levels of cyclosporine (Sandimmune) when both drugs are administered together. Therefore, cyclosporine should be administered two hours before or after orlistat, and more frequent monitoring of cyclosporine levels may be needed.

PREGNANCY: Safe use of orlistat during pregnancy has not been established. Therefore, orlistat is not recommended during pregnancy

NURSING MOTHERS: It is not known if orlistat is secreted in breast milk. Therefore, it probably should not be taken by nursing mothers.

SIDE EFFECTS: The most common side effects of orlistat are oily spotting on underwear, flatulence, urgent bowel movements, fatty or oily stools, increased number of bowel movements, abdominal pain or discomfort, and inability to hold back stool (incontinence). Between 1 in 250 and 1 in 70 patients experienced one or more of these symptoms in the first year. Generally, the side effects occurred within three months of starting therapy. In about 50% of patients, the side effects resolved within one to four weeks, but the effects in some patients lasted six months or longer. To reduce the occurrence of these side effects, meals should contain no more than 30% fat because it is the unabsorbed fat that causes most of the symptoms.

Patients receiving orlistat with a history of oxalate kidney stones may develop increased levels of oxalate in their urine, which may increase the risk of kidney stones.