The short answer
St. John's wort can increase the risk of serotonin syndrome when used with dextroamphetamine. If co-use is necessary, the prescriber may need a lower stimulant starting dose and monitoring, especially when starting or increasing treatment. Do not adjust an existing dose yourself.
What this answer covers
Applies to dextroamphetamine with St. John's wort products; the risk concerns overlapping effects on serotonin.
- Supplement or preparation
- St. John's wort
- Medication ingredient
- dextroamphetamine
Evidence and practical considerations
Side effects & toxicity
Current dextroamphetamine labeling explicitly names St. John's wort as a serotonergic agent and provides management, supporting a clinically major conditional serotonin-toxicity interaction.
- Exact scope
- St. John's wort with dextroamphetamine
- Medication form and route
- systemic dextroamphetamine
- Timing or duration
- Risk is most relevant during overlapping systemic serotonergic exposure and dose initiation or escalation.
What remains uncertain
- Pair-specific incidence and dose-response are unknown.
- A distinct cardiovascular or neuropsychiatric interaction beyond serotonin toxicity was not independently established.
- St. John's wort enzyme induction is not assumed to change dextroamphetamine exposure without exact evidence.
Factors that may matter: higher stimulant dose; other serotonergic drugs or supplements; CYP2D6 inhibitors; history of serotonin toxicity; product variability.
Read the supporting source summaries
Source 1: current United States prescribing information
dailymed.nlm.nih.gov · Source check Jul 24, 2026
Population: Patients receiving dextroamphetamine sulfate.
St. John's wort is explicitly listed as a serotonergic drug; lower initial doses and monitoring are instructed when co-use is warranted.
Pair-specific incidence is not quantified.
Source 2: United States government supplement safety resource
nccih.nih.gov · Source check Jul 24, 2026
Population: Users of St. John's wort and medicines affecting serotonin.
NCCIH warns that combining St. John's wort with serotonin-affecting medicines can cause serious serotonin-related effects.
Not an exact-dextroamphetamine pair study.
Research assessment: · Open full citations ↗
Timing & monitoring
Exact government and regulatory sources support disclosure, avoidance when feasible, and monitoring if concomitant use is clinically warranted.
- Exact scope
- St. John's wort with dextroamphetamine
- Medication form and route
- systemic dextroamphetamine
- Timing or duration
- During overlapping systemic exposure; timing separation is not an adequate risk-control strategy.
What remains uncertain
- This is a pharmacodynamic risk; time separation is not a reliable workaround.
- Use is not automatically prohibited in every circumstance, but requires clinician judgment.
- Enzyme-induction hypotheses are not used for management here.
Factors that may matter: other serotonergic agents; higher dextroamphetamine dose; CYP2D6 inhibitors; product variability.
Read the supporting source summaries
Source 1: United States government drug information
medlineplus.gov · Source check Jul 24, 2026
Population: Patients taking exact dextroamphetamine.
St. John's wort is named and should not be started without discussion.
No dose or interval.
Source 2: current United States prescribing information
dailymed.nlm.nih.gov · Source check Jul 24, 2026
Population: Patients receiving dextroamphetamine sulfate.
St. John's wort is a named serotonergic drug; lower starting dose and monitoring are advised if co-use is warranted.
No evidence that timing separation prevents risk.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Research summary published |
Article revision: 71633cbf265eda3e
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.