Orlistat

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Also indexed as:

Xenical

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

Herbs

Summary of Interactions for Orlistat

Depletion or interference	Beta-carotene Vitamin A Vitamin D Vitamin E
Adverse interaction	None known
Side effect reduction/prevention	Psyllium
Supportive interaction	Food
Reduced drug absorption/bioavailability	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 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

Other Interactions

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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Last Review: 01-21-2009

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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires February 2010.

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