The short answer
A specific St. John’s wort interaction with diflunisal is not established. Have your pharmacist review the exact herb and your full medication list, and remain alert to diflunisal’s own GI risks.
What this answer covers
Oral Hypericum perforatum products with prescription oral diflunisal. Herb interactions with other medicines do not establish a diflunisal interaction.
- Supplement or preparation
- Hypericum perforatum
- Medication ingredient
- diflunisal
The available platelet study is limited
A small study in ten healthy adults found no significant platelet-function change after two weeks of the tested St. John’s wort product. Participants were not taking diflunisal with it. The result does not prove the combination safe or exclude uncommon bleeding.
A broad interaction label is not an exact mechanism
The inspected evidence does not identify a measured St. John’s wort effect on diflunisal levels or a specific new toxicity. Diflunisal’s label describes substantial urinary elimination as glucuronide conjugates. Interactions involving other drugs or other metabolic pathways should not automatically be assigned to this pair.
Review the herb and the whole regimen
Tell your pharmacist the preparation, daily dose and reason for use, as well as your other medicines. The small platelet study does not address all possible drug interactions. There is no established St. John’s wort-specific diflunisal dose adjustment or protective spacing interval in the inspected sources.
Recognize the medicine’s own warning signs
Diflunisal can cause serious stomach or intestinal bleeding even without a supplement. Seek urgent care for vomiting blood or black, tarry stools, and report persistent stomach pain or unusual bleeding. A few hours of separation has not been shown to prevent a combined bleeding effect. Tell your prescriber about other pain relievers, aspirin and anticoagulants.
Evidence and practical considerations
Side effects & toxicity
A specific increase in diflunisal side effects from St. John’s wort has not been established.
- Exact scope
- Oral Hypericum perforatum products with prescription oral diflunisal. Herb interactions with other medicines do not establish a diflunisal interaction. with Exact diflunisal RxCUI 3393 IN, confirmed by current RxNorm. Prescription oral tablets; not aspirin, and not a class-average NSAID effect.
- Medication form and route
- Oral
What remains uncertain
- Small supplement-only platelet study cannot assess exact-pair bleeding, GI injury or drug-level changes. No automatic CYP3A or serotonin-risk transfer.
Factors that may matter: Exact preparation and dose; Fasting versus fed dosing; Bleeding and ulcer history; Other medicines.
Read the supporting source summaries
Source 1: Current prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Prescription oral diflunisal users and healthy-volunteer pharmacology studies.
Diflunisal has dose-dependent reversible platelet effects. At 500 mg twice daily effects were slight; 250 mg twice daily had no measurable effect in a short study. Serious GI bleeding and ulcers remain labeled risks. Antacids may lower levels, especially with continuous use.
How this applies: Exact current drug label. Exact diflunisal RxCUI 3393 IN, confirmed by current RxNorm. Prescription oral tablets; not aspirin, and not a class-average NSAID effect.
Not proof of each supplement combination. Short healthy-volunteer fecal blood-loss findings do not establish long-term GI safety. Aspirin has different platelet pharmacology. No universal antacid separation interval.
Source 2: Original clinical research
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: 10 healthy adults in the original experimental component.
No significant PFA-100 platelet-function change with the tested herbs.
How this applies: Exact drug where specified; other-drug and supplement-only findings remain indirect.
Abstract-only, small sample and laboratory endpoint. No diflunisal co-use; does not exclude bleeding, GI injury or pharmacokinetic interactions.
Source 3: Medication terminology
rxnav.nlm.nih.gov · Source check Sep 10, 2026
Population: Terminology record.
Diflunisal, IN.
How this applies: Exact identity.
No 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: 95f690872800e96d
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.