The short answer
A specific St. John’s wort avoidance or spacing rule with isoniazid has not been established. Review it with the TB team because the full treatment regimen and the herb’s other interactions still matter.
What this answer covers
Hypericum perforatum preparations with variable composition.
- Supplement or preparation
- Hypericum perforatum
- Medication ingredient
- isoniazid
The exact timing evidence is missing
The inspected label and clinical sources did not establish a protective interval or universal requirement to avoid this exact pair. Absence of an established rule is not proof of safety.
Different interactions cannot be substituted
St. John’s wort interacts with several medicines, but a result involving another drug cannot automatically predict isoniazid exposure or define a safe timing gap.
Review the complete regimen
Other TB medicines, prescribed treatments and the exact herbal extract can change the assessment. Isoniazid’s liver warning remains relevant independently of whether this herb is involved.
Coordinate changes with the clinician
Discuss starting or stopping the herb with the prescriber. Do not change isoniazid or choose a spacing schedule on the assumption that it prevents an unmeasured interaction.
Evidence and practical considerations
Timing & monitoring
No exact isoniazid-Hypericum avoidance/timing support identified; other-drug induction and general herbal warnings cannot establish original Q4.
- Exact scope
- Hypericum perforatum preparations with variable composition. with Isoniazid oral tablets.
- Medication form and route
- oral medication; oral supplement
What remains uncertain
- No unmeasured pair incidence, blanket class transfer or arbitrary spacing interval.
Factors that may matter: Preparation; Dose; Other medicines; Organ function.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 11, 2026
Population: People prescribed isoniazid
Hepatitis and peripheral-neuropathy warnings; pyridoxine recommended in predisposed patients; tyramine/histamine food precautions.
How this applies: Exact isoniazid RxCUI 6038 IN, with stated salt/formulation/route bridge.
Exact route and formulation apply. Label precautions do not quantify untested botanical pairs or support arbitrary supplement doses.
Source 2: Federal supplement guidance
nccih.nih.gov · Source check Sep 11, 2026
Population: People considering the named botanical or supplement.
St John’s wort has important interactions with certain medicines. Adult adverse effects include dizziness, restlessness and trouble sleeping.
How this applies: Source applied to isoniazid only with the stated preparation, route and endpoint boundaries.
General St John’s wort interaction guidance; no exact isoniazid spacing/avoidance study. Other-drug enzyme effects cannot establish this pair.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Research summary published | |
| Article prepared | |
| Prepared exact isoniazid article with formulation-specific evidence and uncertainty. |
Article revision: b0de796bc1835461
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.