NutriStack
Amlodipine and Quercetin, a caution.
Quercetin, a flavonoid found in grapefruit and many supplements, inhibits CYP3A4 and intestinal P-glycoprotein in vitro. Amlodipine is a CYP3A4 substrate. However, amlodipine has high inherent oral bioavailability (~65%), making it less susceptible to CYP3A4 inhibition than other calcium channel blockers like nifedipine or felodipine. Clinical studies show grapefruit juice increases amlodipine levels by only 15-20%, producing minimal hemodynamic changes compared to the 100%+ increases seen with felodipine.
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
- Amlodipine and Quercetin
- Pair type
- Caution
- Evidence (highest tier)
- Moderate
- Source citations
- 4 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. Quercetin, a flavonoid found in grapefruit and many supplements, inhibits CYP3A4 and intestinal P-glycoprotein in vitro. Amlodipine is a CYP3A4 substrate. However, amlodipine has high inherent oral bioavailability (~65%), making it less susceptible to CYP3A4 inhibition than other calcium channel blockers like nifedipine or felodipine. Clinical studies show grapefruit juice increases amlodipine levels by only 15-20%, producing minimal hemodynamic changes compared to the 100%+ increases seen with felodipine.
Mechanism. Quercetin and grapefruit furanocoumarins inhibit intestinal CYP3A4 and P-glycoprotein, reducing first-pass metabolism of CYP3A4 substrates. However, amlodipine's already high bioavailability limits the magnitude of this effect. The primary clinical concern is modest blood level increases potentially enhancing amlodipine's vasodilatory effects.
Recommendation. Moderate intake of quercetin supplements or grapefruit is generally acceptable with amlodipine. Avoid excessive grapefruit consumption (more than 1 glass/day) or very high-dose quercetin supplements (>1000 mg/day). Monitor blood pressure if significantly increasing quercetin or grapefruit intake.
Sources (4)
- Josefsson M et al. Effect of grapefruit juice on the pharmacokinetics of amlodipine in healthy volunteers. Eur J Clin Pharmacol. 1996;51(2):189-193. PMID 8911887
- Serban MC, Sahebkar A et al.. Effects of quercetin supplementation on blood pressure: A systematic review and meta-analysis of randomized controlled trials.. Phytotherapy Research. 2024. PMID 41822595
- Pelletier DM, Lacourse R et al.. Quercetin supplementation and exercise performance: A systematic review and meta-analysis.. Nutrients. 2024. PMID 41728031
- Zahedi M, Daryabeygi-Khothehsara R et al.. Effects of quercetin supplementation on glycemic control in patients with type 2 diabetes: A systematic review and meta-analysis.. Phytotherapy Research. 2024. PMID 41516399
Stack Score
How this pair moves the number.
Effect on the composite score
If both Amlodipine 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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