NutriStack
Fexofenadine and Quercetin, a caution.
High-dose quercetin can raise fexofenadine exposure. In a controlled volunteer study, quercetin 500 mg three times daily for 7 days increased fexofenadine AUC by 55% and peak concentration by 68%. Fexofenadine has a wide safety margin, but higher levels may increase headache, dizziness, or drowsiness in sensitive users.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Substances
- Fexofenadine and Quercetin
- Pair type
- Caution
- Evidence (highest tier)
- Moderate
- Source citations
- 2 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Moderate evidence
Caution
What is happening. High-dose quercetin can raise fexofenadine exposure. In a controlled volunteer study, quercetin 500 mg three times daily for 7 days increased fexofenadine AUC by 55% and peak concentration by 68%. Fexofenadine has a wide safety margin, but higher levels may increase headache, dizziness, or drowsiness in sensitive users.
Mechanism. Fexofenadine disposition depends on intestinal and hepatic transporters, including P-glycoprotein and organic anion transporting polypeptides. Quercetin can inhibit P-glycoprotein-mediated efflux, reducing oral clearance and increasing systemic fexofenadine exposure.
Recommendation. Use caution with high-dose quercetin if you also take fexofenadine daily. Keep the quercetin dose consistent and watch for new drowsiness, dizziness, headache, or palpitations after starting it. If side effects appear, stop the quercetin or use a lower-risk allergy plan with your clinician.
Sources (2)
- Kim KA, Park PW, Park JY. Short-term effect of quercetin on the pharmacokinetics of fexofenadine, a substrate of P-glycoprotein, in healthy volunteers. Eur J Clin Pharmacol. 2009;65(6):609-614. PMID 19221726
- Cvetkovic M, Leake B, Fromm MF, Wilkinson GR, Kim RB. OATP and P-glycoprotein transporters mediate the cellular uptake and excretion of fexofenadine. Drug Metab Dispos. 1999;27(8):866-871. PMID 10421612
Stack Score
How this pair moves the number.
Effect on the composite score
If both Fexofenadine and Quercetin are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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