The short answer
St. John’s wort may reduce quinine exposure through enzyme induction. This is an indirect prediction from quinine’s CYP3A4 sensitivity and human herb-probe studies, not a measured effect for this exact pair.
What this answer covers
Hypericum perforatum preparations; hyperforin content and duration vary.
- Supplement or preparation
- Hypericum perforatum
- Medication ingredient
- quinine
Why the interaction is plausible
Quinine labeling describes reduced quinine concentrations with CYP3A4-inducing medicines. Human St. John’s wort studies show induction with some preparations, making reduced quinine exposure a reasonable conditional concern.
The studies used other medicines
The herb studies measured midazolam, not quinine. Quinine results with other inducers cannot supply the magnitude of a St. John’s wort interaction or prove that malaria treatment would fail in a particular person.
Preparation differences are important
A low-hyperforin St. John’s wort preparation had a much smaller probe effect than other preparations. This prevents a uniform prediction for every brand and does not establish reduced intestinal absorption.
Coordinate starting or stopping
Have the prescriber review the herb before use during quinine treatment. Do not increase quinine to compensate or assume a few hours of separation prevents enzyme induction. Report worsening illness promptly.
Evidence and practical considerations
Absorption & effectiveness
Conditional reduced exposure/effectiveness via induction based on exact quinine label and indirect human St John’s wort probe studies. No direct herb-pair effect size, reduced gut absorption or validated spacing.
- Exact scope
- Hypericum perforatum preparations; hyperforin content and duration vary. with Quinine sulfate oral capsules, not quinidine or homeopathic products.
- 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 quinine
Aluminum/magnesium antacids may delay/decrease absorption; avoid coadministration. Sodium bicarbonate may increase plasma quinine through urinary alkalinization. Immune thrombocytopenia is a separate serious risk.
How this applies: Exact quinine RxCUI 9071 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: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 11, 2026
Population: 12 healthy adults.
Short-term dosing had no measured CYP effect; repeated use reduced oral midazolam AUC more than IV AUC.
How this applies: Original source interpreted for quinine only within the stated preparation and endpoint limits.
Not a direct quinine combination trial; original preparation, dose and endpoint limits apply. No exact-pair adverse-event rate or protective spacing established.
Source 3: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 11, 2026
Population: 20 healthy men.
Small AUC decrease considered not clinically relevant by authors; no significant Cmax or half-life change.
How this applies: Original source interpreted for quinine only within the stated preparation and endpoint limits.
Not a direct quinine combination trial; original preparation, dose and endpoint limits apply. No exact-pair adverse-event rate or protective spacing established.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Research summary published | |
| Editorial update | |
| Corrected missing spaces between numbers and units or words in the copy before registration; evidence and conclusions unchanged. | |
| Article prepared | |
| Prepared exact quinine article with formulation-specific evidence and uncertainty. |
Article revision: 0535cb5bcb55b558
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.