From the databaseWhat the row says.
Every entry follows the same shape: what is happening, the mechanism, and the recommendation.
Scope
Supplement × Prescription
Last verified
June 4, 2026
ContraindicatedModerate evidence
What is happening. St. John's Wort can induce drug-metabolizing enzymes and transporters and may lower Voriconazole exposure or undermine therapy.
Mechanism. Hyperforin induces CYP3A4 and P-glycoprotein, which can reduce exposure to susceptible drugs.
Recommendation. Avoid St. John's Wort with Voriconazole.
Stack Score
How it moves the number.
Effect on the composite score
If both St. John's Wort and Voriconazole are in the same stack, this pair applies −25 to your Stack Score (per scored contraindication row).
The full algorithm, the clamping rules, and four worked stacks are at /methodology/stack-score.
SourcesSources, by evidence tier.
Every claim on this page is cited. PMIDs link straight to PubMed.
Reference material
1- 1Izzo AA, Ernst E. Interactions between herbal medicines and prescribed drugs: an updated systematic review. Drugs. 2009.Needs sourceNo link