Fexofenadine

Also indexed as: Allegra®, Telfast®

Combination drug: Allegra®-D

Fexofenadine is a selective antihistamine used to relieve allergic rhinitis (seasonal allergy) symptoms including sneezing, runny nose, itching, and watery eyes. Fexofenadine is available alone and in a combination product.

Summary of Interactions with Vitamins, Herbs, and Foods
In some cases, a 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.

Avoid: Adverse interaction—Avoid these supplements when taking this medication because taking them together may cause undesirable or dangerous results.	Grapefruit juice
Check: Other—Before taking any of these supplements or eating any of these foods with your medication, read this article in full for details.	St. John's wort
Depletion or interference	None known
Side effect reduction/prevention	None known
Supportive interaction	None known
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 Herbs

St. John's Wort
In a study of healthy volunteers, administration of 900 mg of St. John's wort one hour prior to fexofenadine resulted in a significant increase in blood levels of fexofenadine, compared with the blood levels after taking fexofenadine alone.¹ On the other hand, long-term administration of St. John's wort (300 mg three times per day for two weeks) did not alter blood levels of fexofenadine. Until more is known, St. John's wort should not be combined with fexofenadine, except under the supervision of a doctor.

Interactions with Foods and Other Compounds

Food
Ingestion of grapefruit juice, orange juice, or apple juice along with fexofenadine decreases blood levels of the drug.² ³

Alcohol
Selective antihistamines, including fexofenadine, may cause drowsiness or dizziness; however, it is less likely than with nonselective antihistamines.⁴ Alcohol can intensify drowsiness and dizziness, increasing the risk of accidental injury.

References
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1. Wang Z, Hamman MA, Huang SM, et al. Effect of St John's wort on the pharmacokinetics of fexofenadine. Clin Pharmacol Ther 2002;71:414–20.

2. Dresser GK, Bailey DG, Leake BF, et al. Fruit juices inhibit organic anion transporting polypeptide-mediated drug uptake to decrease the oral availability of fexofenadine. Clin Pharmacol Ther 2002;71:11–20.

3. Dresser GK, Kim RB, Bailey DG. Effect of grapefruit juice volume on the reduction of fexofenadine bioavailability: possible role of organic anion transporting polypeptides. Clin Pharmacol Ther 2005;77:170–7.

4. Threlkeld DS, ed. Respiratory Drugs, Antihistamines. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, May 1998, 194c.

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The information presented in Healthnotes 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 chemist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires March 2007.

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Interactions with Herbs

Interactions with Foods and Other Compounds