Supplements
quercetin inhibits CYP3A4
In plain terms: Can quercetin interfere with prescription medications?
Part of: 🧪 quercetin
It blocks the CYP3A4 enzyme in the lab, and raises drug levels in rats. Whether that happens in people at supplement doses is untested, and in the one direct check the effect did not even carry across two similar drugs. Mention it to your prescriber if you take a narrow-margin medication.
📅 Last reviewed: 2026-07-26 ⓘ
Evidence ladder
How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."
Top evidence so far: Animal studies (Animal)
How the studies fall
What the evidence shows
The enzyme inhibition itself is solid: two independent in-vitro assays converge on quercetin inhibiting CYP3A4 with IC50 around 18-55 micromolar, and rat studies show it raises exposure to co-administered substrates (ziprasidone, amiodarone, palbociclib). What is NOT established is clinical relevance in people. There is no human interaction study at all.
The evidence (6)
| Source | Grade | Stance | Quality | Finding |
|---|---|---|---|---|
| Tang H et al 2023 · study_type: in-vitro | in-vitro | supports | moderate | In breast cancer cell lines, quercetin down-regulated CYP3A4 expression and reduced its enzymatic conversion of arachidonic acid to EETs (measured by Western blot and LC-MS/MS), blocking downstream Stat3 nuclear translocation and tumor grow |
| Zhou Q et al 2025 · study_type: animal | animal | supports | high | Quercetin inhibited CYP3A4-mediated ziprasidone metabolism in vitro (rat/human liver microsomes and CYP3A4 baculosomes) with IC50 = 17.59±1.01 μM for wild-type CYP3A4.1 (up to 54.51±1.35 μM for the CYP3A4.33 variant, mixed-mechanism inhibit |
| Ahmad E et al 2023 · study_type: animal | animal | supports | moderate | In rats, 14-day quercetin pretreatment (20 mg/kg/day) before a single amiodarone dose (a CYP3A4/CYP2C9/CYP2D6 substrate) increased amiodarone Cmax by 45.5% and AUC by 13.7%, while single-dose coadministration raised Cmax by 12.9% and AUC by |
| Vieira CSP et al 2025 · study_type: in-vitro | in-vitro | supports | high | A high-throughput fluorimetric microsomal assay found quercetin inhibited CYP3A4 with IC50 = 23±5 μmol/L, one of the more potent of 15 tested polyhydroxyflavonoids (baicalein/scutellarein were stronger at IC50 15-19 μM), with docking showin |
| Ahmad E et al 2023 · Current drug safety | animal | supports | moderate | In rats, 14-day oral quercetin pretreatment increased warfarin Cmax by 30.43%, AUC0-∞ by 62.94%, t1/2 by 10.54%, and decreased clearance by 41.35% vs control (single co-administration: Cmax +10.98%, AUC +20.20%). Warfarin is stated as metab |
| Patil PH et al 2024 · study_type: animal | animal | mixed | moderate | In vitro (rat liver microsomes and Caco-2 cells), quercetin significantly inhibited both intestinal efflux and CYP3A4-mediated metabolism of the CYP3A4 substrates palbociclib and ribociclib (P<.05); but in vivo in rats, quercetin pretreatme |
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