The short answer
St. John’s wort may lower dexamethasone exposure through enzyme induction. Have starting or stopping it reviewed by the prescriber; the size of the effect has not been measured for this exact combination.
What this answer covers
Oral dexamethasone with Hypericum perforatum preparations containing enzyme-inducing constituents. Hyperforin exposure varies across products.
- Supplement or preparation
- Hypericum perforatum
- Medication ingredient
- dexamethasone
Which treatment this applies to
This review applies to systemic oral dexamethasone tablets. Dose, treatment duration and the condition being treated matter. It does not establish the same exposure or supplement interaction for an injection, eye preparation or skin product.
Why steroid exposure could fall
The dexamethasone label states that CYP3A4 inducers can increase its metabolism and may require clinical dose adjustment. This is a metabolism concern; it does not mean the supplement binds dexamethasone in the gut or proves treatment failure.
The human supplement evidence is product-dependent
In a study of 42 healthy men, six Hypericum preparations lowered exposure to the probe medicine midazolam after repeated use. Higher hyperforin products had larger effects. The study did not administer dexamethasone, so its percentages cannot be used to calculate a steroid dose change.
Coordinate both starting and stopping
Show the exact preparation and daily dose to the prescriber, including a product you intend to stop. They can assess disease control and whether treatment needs adjustment. A few hours of separation is not a validated solution to enzyme induction, and you should not change the steroid or its taper yourself.
Evidence and practical considerations
Absorption & effectiveness
Dexamethasone CYP3A4 susceptibility plus human Hypericum probe studies support a conditional reduced-exposure concern, not a proven absorption loss or fixed dose adjustment.
- Exact scope
- Oral dexamethasone with Hypericum perforatum preparations containing enzyme-inducing constituents. Hyperforin exposure varies across products. with Exact RxNorm 3264 IN dexamethasone; plain oral tablets. Injectable phosphate and other route/formulation exposures are not treated as identical.
- Medication form and route
- Oral
What remains uncertain
- Exact-drug enzyme susceptibility plus indirect human probe evidence. No exact combination PK trial, transferable percentage, demonstrated gut absorption loss or validated spacing.
Factors that may matter: Exact oral preparation and dose; Treatment duration and indication; Blood pressure and electrolyte status; Other medicines.
Read the supporting source summaries
Source 1: Current prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed Dexamethasone oral tablets.
Describes CYP3A4 substrate interactions, systemic bone effects and dose-dependent electrolyte precautions. Synthetic steroid salt/potassium effects are less likely except at large doses.
How this applies: Exact ingredient and specified formulation. Exact RxNorm 3264 IN dexamethasone; plain oral tablets. Injectable phosphate and other route/formulation exposures are not treated as identical.
No universal mineral requirement or same-milligram equivalence to other glucocorticoids; oral CYP effects are not automatically topical or injection effects.
Source 2: Original clinical research
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: 42 healthy men assigned six Hypericum preparations.
All tested products lowered midazolam exposure, with a much larger effect for high hyperforin.
How this applies: Applicable only to the stated preparation, route and endpoints; other-drug evidence is indirect.
Abstract-only; not dexamethasone, no transferable percentage or patient outcome, and product-dependent effects.
Source 3: Medication terminology
rxnav.nlm.nih.gov · Source check Sep 10, 2026
Population: Terminology.
dexamethasone 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: e3a6d20a9461ded1
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.