NutriStack
Quercetin and Verapamil, a caution.
In rabbits, quercetin roughly doubled both the Cmax and AUC of verapamil by inhibiting CYP3A4 and P-glycoprotein. Verapamil already has a narrow therapeutic window for bradycardia and AV block, so high-dose quercetin supplements layered onto verapamil could meaningfully amplify rate suppression, hypotension, or constipation.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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What the row says.
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At a glance
- Pair type
- Caution
- Evidence (highest tier)
- Emerging
- 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 · Emerging evidence
Caution
What is happening. In rabbits, quercetin roughly doubled both the Cmax and AUC of verapamil by inhibiting CYP3A4 and P-glycoprotein. Verapamil already has a narrow therapeutic window for bradycardia and AV block, so high-dose quercetin supplements layered onto verapamil could meaningfully amplify rate suppression, hypotension, or constipation.
Mechanism. Quercetin inhibits CYP3A4-mediated N-demethylation of verapamil and blocks intestinal P-gp efflux, raising oral bioavailability and slowing systemic clearance.
Recommendation. Avoid high-dose quercetin supplements (over 500 mg/day) while on verapamil. If used, separate doses by at least 4 hours, monitor pulse and blood pressure twice daily for 2 weeks, and stop quercetin if your HR drops below 50 bpm or you become lightheaded.
Minimum separation. 240
Sources (2)
- Choi JS, Han HK. The effect of quercetin on the pharmacokinetics of verapamil and its major metabolite, norverapamil, in rabbits. J Pharm Pharmacol. 2004;56(12):1537-42. PMID 15563760
- Mills TA, Kawji MM, Cataldo VD, et al. Profound sinus bradycardia due to diltiazem, verapamil, and/or beta-adrenergic blocking drugs. J La State Med Soc. 2004;156(6):327-31. PMID 15688675
Stack Score
How this pair moves the number.
Effect on the composite score
If both Quercetin and Verapamil 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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