The short answer
St. John’s wort can stimulate drug metabolism and may lower diltiazem exposure. Have the prescriber review it before starting or stopping; a dose gap is not an established solution.
What this answer covers
Oral diltiazem with Hypericum perforatum products capable of CYP3A induction. Hyperforin content varies; a midazolam probe study is indirect evidence.
- Supplement or preparation
- Hypericum perforatum
- Medication ingredient
- diltiazem
Why reduced exposure is plausible
Diltiazem’s label reports that rifampin lowered its concentrations to undetectable levels and advises avoiding known CYP3A4 inducers. St. John’s wort can induce that metabolic pathway in people. This is a metabolism concern, not evidence that the herb physically blocks diltiazem absorption.
The human herb study used another medicine
In 42 healthy men, six St. John’s wort products reduced exposure to the CYP3A probe midazolam after two weeks. The effect was much larger with higher hyperforin content. Those percentages cannot be applied to diltiazem, and lower-hyperforin products were not interaction-free in that study.
A product label needs close review
Bring the extract name, dose, hyperforin information and all combination ingredients. An unspecified brand cannot establish the degree of induction. Discuss both starting and stopping with the prescriber because medication exposure may change as the inducing effect develops or wears off. No fixed gap was validated.
Monitor the condition being treated
Keep the agreed BP or angina monitoring plan and report poorer control. Do not increase diltiazem to compensate for a supplement or stop either treatment without advice. The clinician can choose an alternative supplement or treatment approach using your exact formulation and indication.
Evidence and practical considerations
Absorption & effectiveness
The exact diltiazem label advises avoiding CYP3A4 inducers, while human Hypericum studies demonstrate product-dependent induction; the expected exposure concern is conditional and not directly quantified for this pair.
- Exact scope
- Oral diltiazem with Hypericum perforatum products capable of CYP3A induction. Hyperforin content varies; a midazolam probe study is indirect evidence. with Current RxNorm confirms diltiazem RxCUI 3443 IN. Oral hydrochloride once-daily capsules; immediate-release single-dose originals explicitly distinguished. No transfer to topical fissure treatment or IV administration.
- Medication form and route
- Oral
What remains uncertain
- Exact-drug inducer label plus indirect human probe study. No direct diltiazem-Hypericum magnitude, clinical failure rate or validated spacing; product-dependent induction retained.
Factors that may matter: Exact preparation and dose; Oral formulation; Blood pressure and pulse; Other medicines.
Read the supporting source summaries
Source 1: Current prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed diltiazem hydrochloride extended-release capsules.
Avoid known CYP3A4 inducers: rifampin lowered concentrations to undetectable. Bradycardia, conduction and hypotension warnings apply.
How this applies: Exact ingredient through the stated labeled salt and oral formulation. Current RxNorm confirms diltiazem RxCUI 3443 IN. Oral hydrochloride once-daily capsules; immediate-release single-dose originals explicitly distinguished. No transfer to topical fissure treatment or IV administration.
Other-drug inducer magnitudes not transferred. Guggul eight-hour sampling is not spacing; small conflicting grapefruit juice studies retained.
Source 2: Original clinical research
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: 42 healthy men assigned six Hypericum preparations.
Midazolam AUC fell with all tested preparations, most with high hyperforin; the effect varied markedly by product.
How this applies: Exact preparation and endpoint boundaries retained; this is not a measured diltiazem combination unless explicitly stated.
Abstract-only; midazolam is not diltiazem. Effect magnitude and clinical consequences cannot transfer; low-hyperforin product still showed a smaller effect.
Source 3: Medication terminology
rxnav.nlm.nih.gov · Source check Sep 10, 2026
Population: Terminology.
diltiazem is IN.
How this applies: Exact ingredient.
Not clinical evidence.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Sources checked and article drafted. | |
| Research summary published |
Article revision: 260c759fe4ec0683
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.