The short answer
Review St John’s wort with perphenazine because both have photosensitivity precautions. The added skin-reaction risk has not been measured, and reduced perphenazine absorption is not established.
What this answer covers
Oral perphenazine with the exact supplement preparation described.
- Supplement or preparation
- Hypericum perforatum
- Medication ingredient
- perphenazine
Light sensitivity is a conditional concern
Perphenazine labeling advises avoiding undue sun exposure. Human St John’s wort phototesting found modest effects with some higher-dose or repeated regimens, while other specified extracts did not change the mean light-response threshold. These findings do not quantify the effect of taking both products.
Use the exact medicine’s evidence
Perphenazine pharmacokinetics vary with CYP2D6 activity. A study of a different enzyme therefore cannot establish reduced perphenazine exposure.
Product and exposure matter
The phototests used defined extracts and controlled ultraviolet exposure. They do not show that every dose or brand causes an additive rash, and there is no tested protective interval. Follow the medicine’s sun precautions and ask about the actual extract.
Coordinate changes with the prescriber
Discuss the actual extract, dose and reason for use before changing either product. Do not increase or stop perphenazine to compensate for a predicted interaction that has not been established for the combination.
Evidence and practical considerations
Absorption & effectiveness
Review St John’s wort with perphenazine because both have photosensitivity precautions. The added skin-reaction risk has not been measured, and reduced perphenazine absorption is not established.
- Exact scope
- Oral perphenazine with the exact supplement preparation described. with Oral perphenazine with the stated label and formulation limits.
- Medication form and route
- oral
What remains uncertain
- Original exact-pair exposure, toxicity and timing propositions insufficient unless individually specified below. Human CYP3A4 probe induction does not establish the target medicine concentration or clinical response. No protective gap or automatic dose adjustment. Q3 narrower photosensitivity precaution conditional; positive and null standalone human phototests retained; Q2 insufficient.
Factors that may matter: Exact preparation and amount; Other medicines; Seizure history, alertness or electrolyte status where relevant.
Read the supporting source summaries
Source 1: Current U.S. regulatory product labeling
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed oral perphenazine.
May cause initial drowsiness although hypnotic effects are described as minimal. Photosensitivity and anticholinergic effects are possible. Pharmacokinetics covary with CYP2D6 activity.
How this applies: Exact ingredient and oral-route clinical context.
Label class warnings do not establish every exact botanical interaction, event rate or protective supplement interval.
Source 2: Federal supplement guidance
nccih.nih.gov · Source check Sep 10, 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: Selected medicine interactions and supplement adverse effects do not prove every antipsychotic exposure or sedation claim.
General guidance does not quantify this exact medication combination or establish a universal protective interval.
Source 3: Original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Twelve older adults in a supplement and enzyme-probe study.
St John’s wort increased CYP3A4 probe activity, with no significant CYP1A2 or CYP2D6 effect identified for that herb.
How this applies: Mechanistic human context with exact substrate limits.
No target antipsychotic was administered. Results depend on extract and enzyme substrate; CYP3A4 induction does not establish CYP2D6-driven medicine loss of effect.
Source 4: Original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Healthy volunteers in single-dose and repeated-dose extract studies.
Single-dose simulated sunlight sensitivity did not significantly change; high-dose or repeated exposure produced modest changes in selected ultraviolet measures.
How this applies: Supports a conditional photosensitivity concern rather than a quantified exact interaction.
No perphenazine co-use, high and preparation-specific exposure; laboratory light threshold is not clinical rash incidence.
Source 5: Original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Healthy men in two open prospective studies.
Mean minimal erythema dose did not change significantly after treatment; individual photosensitivity could not be ruled out.
How this applies: Retains contrary preparation-specific original human findings.
Small open studies, specific products, no perphenazine co-use.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Initial source-checked draft with exact preparation limits, original study findings and uncertainty. Clinical review not recorded. | |
| Research summary published |
Article revision: f1a5e86db1fa09b3
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.