The short answer
The theophylline label warns against St. John’s wort co-use. If you already take both, consult the prescriber before stopping the herb because theophylline levels may rise.
What this answer covers
Hypericum perforatum; preparation, hyperforin content, duration and start/stop history matter.
- Supplement or preparation
- Hypericum perforatum
- Medication ingredient
- theophylline
Follow the exact medicine warning
The label says St. John’s wort may lower theophylline levels. It also warns that levels may rise when the herb is stopped. Ask for a plan that may include a blood level rather than changing either treatment yourself.
A small trial found no change
Twelve healthy men took one St. John’s wort preparation for fifteen days, with a single oral theophylline dose. Plasma drug measurements did not change significantly. This limits certainty about the size of the effect across products.
Timing is about more than swallowing together
The label’s warning should not be read as permission to take the products several hours apart. No tested clock gap is supplied, and starting or stopping a regular herbal product can matter beyond a single dose.
Recognize possible toxicity
Contact the prescriber promptly for repeated nausea or vomiting, new insomnia or tremor after a product change. A seizure, fainting or a sustained rapid or irregular heartbeat needs urgent assessment. A blood theophylline measurement may be needed; symptoms alone cannot determine the level.
Evidence and practical considerations
Absorption & effectiveness
The current exact label supports a clinically actionable interaction precaution and supervised discontinuation. Reduced levels are not established as universal or as impaired gut absorption; a small original human trial found no plasma pharmacokinetic change.
- Exact scope
- Hypericum perforatum; preparation, hyperforin content, duration and start/stop history matter. with Exact theophylline anhydrous extended-release tablets and oral solution. Exact RxNorm IN10438. Oral anhydrous theophylline formulations distinguished; intravenous and aminophylline study exposures are identified separately.
- Medication form and route
- oral
- Timing or duration
- Source-specific single-dose, repeated-dose and observational exposures distinguished.
What remains uncertain
- One negative fifteen-day preparation-specific study does not overturn labeling or establish safe dosing. No validated protective separation interval.
Factors that may matter: preparation and plant part; clinical indication; dose; other medicines; baseline alertness.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed theophylline.
Variable clearance, narrow therapeutic range and serum concentration monitoring; toxicity can include arrhythmias and seizures; label specifically warns about St John’s wort and ephedrine.
How this applies: Exact RxNorm IN10438. Oral anhydrous theophylline formulations distinguished; intravenous and aminophylline study exposures are identified separately.
No universal supplement dose, interval, event rate or untested formulation equivalence.
Source 2: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed theophylline.
Variable clearance, narrow therapeutic range and serum concentration monitoring; toxicity can include arrhythmias and seizures; label specifically warns about St John’s wort and ephedrine.
How this applies: Exact RxNorm IN10438. Oral anhydrous theophylline formulations distinguished; intravenous and aminophylline study exposures are identified separately.
No universal supplement dose, interval, event rate or untested formulation equivalence.
Source 3: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Twelve healthy Japanese men in randomized crossover study.
No significant change in plasma theophylline pharmacokinetics.
How this applies: Only the named drug, preparation, route and measured endpoints apply.
One short exposure and one preparation; not proof all extracts are safe or reason to dismiss the current label warning.
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 | |
| Current exact available claims adjudicated using original captures and explicit identity and comparator limits. |
Article revision: 097f88b5373a7160
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.