Drug Interaction Report

Felodipine and St John's Wort: Interaction Details

A pharmacist-reviewed analysis of the Felodipine and St John's Wort interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

St John's Wort

No brand names on record
+

Felodipine

Plendil®
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Major
Potentially serious — often needs a change or close monitoring.
How we grade severity & evidence

Severity levels

  • Contraindicated: These should generally not be used together.
  • Major: Potentially serious — often needs a change or close monitoring.
  • Moderate: Can be significant — usually manageable with monitoring.
  • Minor: Usually limited clinical impact.

Evidence grades

  • Established: Well documented — supported by controlled studies or strong clinical data.
  • Probable: Good supporting evidence, though not definitively proven.
  • Suspected: Some evidence suggests this interaction, but it is not well established.
  • Possible: Limited or conflicting evidence; the interaction may occur.
  • Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.

Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.

Of 125 documented Felodipine interactions, 83 are rated major — including this one.
Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.
Onset
unspecified
Evidence
theoretical
Severity
Major

What happens

Reduced felodipine plasma concentrations and antihypertensive efficacy

Interaction Deep Dive

Concomitant use of felodipine (a CYP3A4 substrate)1 and St John's Wort (a CYP3A4 inducer) 34 may decrease felodipine plasma levels and may result in a reduction of antihypertensive efficacy. Although not studied with felodipine, the concomitant use of St. John's wort and nifedipine (another calcium channel blocker) reduced the mean plasma concentration of nifedipine by 53% at 30 minutes in an open trial of 22 healthy subjects 2. Coadministration of felodipine and St John's Wort requires caution and blood pressure should be monitored.

Why it happens (mechanism)

Induction of CYP3A4-mediated metabolism of felodipine by St John's Wort

Literature reports

1 report — tap to read

a) Although not studied with felodipine, the concomitant use of St. John's wort and nifedipine (another calcium channel blocker) reduced the mean plasma concentration of nifedipine by 53% at 30 minutes in an open trial of 22 healthy subjects. Subjects received St. John's wort 900 mg daily for 18 days and then received a single dose of nifedipine 10 mg orally. Mean plasma concentration of nifedipine at 30 minutes was reduced by 53% versus nifedipine alone (statistical significance not stated) 2.

Common questions

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

Reduced felodipine plasma concentrations and antihypertensive efficacy Always confirm with your pharmacist or prescriber before making any change.

How serious is the Felodipine and St John's Wort interaction?

It is rated major. Potentially serious — often needs a change or close monitoring.

How quickly could this interaction happen?

The documented onset is "unspecified". The timing of this interaction is not well characterized.

How strong is the evidence for this interaction?

The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.

Questions for your pharmacist

  • Does my dose of Felodipine or St John's Wort need adjusting while I take them together?
  • What symptoms should prompt me to call you or my prescriber right away?
  • Does the timing of my doses matter for this combination?
  • Is there a safer alternative to one of these medications for me?

References (4)

  1. Product Information: PLENDIL(R) extended-release oral tablets, felodipine extended-release oral tablets. AstraZeneca LP, Wilmington, DE, 2003. DailyMed
  2. Smith M, Lin KM, & Zheng YP: An open trial of nifedipine-herb interactions: nifedipine with St. John's Wort, ginseng, or Ginkgo biloba (abstract). Clin Pharmacol Ther 2001; 69(2):P86.
  3. Gurley BJ, Gardner SF, Hubbard MA, et al: Cytochrome P450 phenotypic ratios for predicting herb-drug interactions in humans. Clin Pharmacol Ther 2002; 72(3):276-287. PubMed
  4. Roby CA, Anderson GD, Kantor E, et al: St. John's Wort: effect on CYP3A4 activity. Clin Pharmacol Ther 2000; 67:451-457. DOI
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St John's Wort

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Felodipine

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Beyond drug–drug

These medications also interact with supplements

Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:

Felodipine + Activated Charcoal American Hellebore American Mistletoe Coleus Grapefruit St. John's Wort Tyramine Wine + 224 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

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This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.