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Orlistat

Also indexed as: Xenical

Illustration

Orlistat is used for obesity management, including weight loss and weight maintenance, in association with a low-calorie diet.

Summary of Interactions with Vitamins, Herbs, and Foods
In some cases, an herb or supplement may appear in more than one category, which may seem contradictory. For clarification, read the full article for details about the summarized interactions.

Beneficial May Be Beneficial: Depletion or interference—The medication may deplete or interfere with the absorption or function of the nutrient. Taking these nutrients may help replenish them.

Beta-carotene

Vitamin A

Vitamin D

Vitamin E

Beneficial May Be Beneficial: Side effect reduction/prevention—Taking these supplements may help reduce the likelihood and/or severity of a potential side effect caused by the medication.

Psyllium

Beneficial May Be Beneficial: Supportive interaction—Taking these supplements may support or otherwise help your medication work better.

Food

Reduced drug absorption/bioavailability

None known

Adverse interaction

None known

An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.

Interactions with Dietary Supplements

Beta-carotene
One well-controlled study showed that taking orlistat greatly reduces the absorption of beta-carotene.1 Therefore, individuals taking orlistat for long periods of time should probably supplement with beta-carotene.

Vitamin E
Taking orlistat dramatically reduces the absorption of vitamin E,2 which might result in deficiency symptoms. Therefore, people taking orlistat for long periods of time should supplement with vitamin E.

Vitamin A and Vitamin D
In one well-controlled study, taking orlistat for six months resulted in reduced blood levels of vitamins A and D, though levels for most individuals remained within the normal range. However, a few people developed levels low enough to require supplementation.3 Other studies have shown that taking orlistat had no affect on blood vitamin A levels.4 5 Although additional research is needed, the current evidence suggests that individuals taking orlistat for more than six months should supplement with vitamins A and D.

Interactions with Herbs

Psyllium
In a group of obese women taking orlistat three times per day, ingestion of 6 grams of psyllium with each dose of orlistat significantly reduced the gastrointestinal side effects of the drug.6

Interactions with Foods and Other Compounds

Food
Orlistat blocks enzymes responsible for the breakdown and absorption of fat. Therefore, orlistat should be taken during, or up to one hour after, each main meal that contains fat.7

References:

1. Zhi J, Melia AT, Koss-Twardy SG, et al. The effect of orlistat, an inhibitor of dietary fat absorption, on the pharmacokinetics of beta-carotene in healthy volunteers. J Clin Pharmacol 1996;36:152–9.

2. Sifton DW, ed. Physicians’ Desk Reference. Montvale, NJ: Medical Economics Company, Inc., 2000, 2693–6.

3. Van Gaal LF, Broom JI, Enzi G, Toplak H. Efficacy and tolerability of orlistat in the treatment of obesity: a 6-month dose ranging study. Orlistat Dose-Ranging Study Group. Eur J Clin Pharmacol 1998;54:125–32.

4. Melia AT, Koss-Twardy SG, Zhi J. The effect of orlistat, an inhibitor of dietary fat absorption, on the absorption of vitamins A and E in healthy volunteers. J Clin Pharmacol 1996;36:647–53.

5. James WP, Aveell A, Broom J, Whitehead J. A one-year trial to assess the value of orlistat in the management of obesity. Int J Obes Relat Metab Disord 1997;21 Suppl 3:S24–30.

6. Cavaliere H, Floriano I, Medeiros-Neto G. Gastrointestinal side effects of orlistat may be prevented by concomitant prescription of natural fibers (psyllium mucilloid). Int J Obes Relat Metab Disord 2001;25:1095–9.

7. Sifton DW, ed. Physicians’ Desk Reference. Montvale, NJ: Medical Economics Company, Inc., 2000, 2693–6.

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