What kind of interaction is it?

Conflict: combining the two is generally not recommended without clinician oversight.

Is this interaction backed by published research?

Yes. NutriStack lists 3 citation rows for the Felodipine + St. John's Wort pair, each linking to PubMed by PMID where available. Full sourcing methodology at https://nutristackapp.com/methodology/interactions.

Supplement × Prescription·a conflict·Strong evidence

Felodipine + St. John's Wort

Q: Can I take Felodipine and St. John's Wort together?

Generally not recommended together. Felodipine and St. John's Wort have a documented conflict. St. John's Wort is a potent inducer of intestinal and hepatic CYP3A4, the primary enzyme that metabolizes felodipine, which already has very low oral bioavailability (about 15 percent) because of extensive first-pass metabolism. Concomitant use markedly lowers felodipine plasma concentrations and can result in loss of antihypertensive control.

Q: How does this affect a NutriStack Stack Score?

-10 to your Stack Score per scored conflict row.

Conflict Strong evidence

St. John's Wort is a potent inducer of intestinal and hepatic CYP3A4, the primary enzyme that metabolizes felodipine, which already has very low oral bioavailability (about 15 percent) because of extensive first-pass metabolism. Concomitant use markedly lowers felodipine plasma concentrations and can result in loss of antihypertensive control.

Supplement × Prescription

Open the interaction checker → Read the methodology

From the database

What the row says.

Every entry follows the same shape: what is happening, the mechanism, and the recommendation.

Substances

Felodipine and St. John's Wort

Pair type

Conflict, Caution

Evidence

Strong

Source citations

Scope

Supplement × Prescription

Last verified

June 4, 2026

ConflictStrong evidence

What is happening. St. John's Wort is a potent inducer of intestinal and hepatic CYP3A4, the primary enzyme that metabolizes felodipine, which already has very low oral bioavailability (about 15 percent) because of extensive first-pass metabolism. Concomitant use markedly lowers felodipine plasma concentrations and can result in loss of antihypertensive control.

Mechanism. Hyperforin in St. John's Wort activates the pregnane X receptor, upregulating CYP3A4 (and P-glycoprotein), which accelerates presystemic and hepatic metabolism of felodipine and reduces its systemic exposure.

Recommendation. Avoid combining St. John's Wort with felodipine. If a patient is already taking St. John's Wort, do not start it during felodipine therapy, and if it must be stopped, monitor blood pressure closely for several weeks because enzyme induction reverses slowly. Discuss alternatives with the prescriber.

CautionModerate evidence

What is happening. St. John's Wort can induce drug-metabolizing enzymes and transporters and may lower Felodipine exposure or undermine therapy.

Mechanism. Hyperforin induces CYP3A4 and P-glycoprotein, which can reduce exposure to susceptible drugs.

Recommendation. Avoid starting or stopping St. John's Wort without prescriber review while taking Felodipine.

Stack Score

How it moves the number.

Effect on the composite score

If both Felodipine and St. John's Wort are in the same stack, this pair applies −10 to your Stack Score (per scored conflict row).

The full algorithm, the clamping rules, and four worked stacks are at /methodology/stack-score.

Sources

Sources, by evidence tier.

Every claim on this page is cited. PMIDs link straight to PubMed.

Reference material

1Izzo AA, Ernst E. Interactions between herbal medicines and prescribed drugs: an updated systematic review. Drugs. 2009.Needs sourceNo link
2Madabushi R, Frank B, Drewelow B, et al. Hyperforin in St. John's wort drug interactions. Eur J Clin Pharmacol. 2006.Needs sourceNo link
3Mannel M. Drug interactions with St John's wort: mechanisms and clinical implications. Drug Saf. 2004.Needs sourceNo link

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