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Orlistat

Also indexed as: Xenical®

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

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 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.6

Summary of Interactions for Orlistat

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

For the convenience of the reader, the information in the summary is categorized as follows: “Depletion or interference” indicates the drug may deplete or interfere with the absorption or function of the supplement or herb. “Adverse interaction” indicates that the supplement or herb used together with the drug may result in undesirable effects. “Side effect reduction/prevention” indicates the supplement or herb may reduce the likelihood and/or severity of a potential side effect caused by the drug. “Supportive interaction” indicates the supplement or herb may support or aid the function of the drug. “Reduced drug absorption/bioavailability” indicates that the supplement or herb may decrease the absorption and/or activity of the drug in the body. An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.

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