NutriStack
Dabigatran and St. John's Wort, a conflict.
St. John's wort is a potent P-glycoprotein and CYP3A4 inducer. Because dabigatran etexilate's oral absorption depends on P-gp, induction can substantially lower dabigatran plasma levels, potentially making it ineffective and increasing the risk of stroke or thromboembolism. The manufacturer specifically advises avoiding the combination.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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What the row says.
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At a glance
- Substances
- Dabigatran and St. John's Wort
- Pair type
- Conflict
- Evidence (highest tier)
- Moderate
- Source citations
- 2 sources
- Stack Score effect
- −10 to your Stack Score (per scored conflict row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Conflict · Moderate evidence
Conflict
What is happening. St. John's wort is a potent P-glycoprotein and CYP3A4 inducer. Because dabigatran etexilate's oral absorption depends on P-gp, induction can substantially lower dabigatran plasma levels, potentially making it ineffective and increasing the risk of stroke or thromboembolism. The manufacturer specifically advises avoiding the combination.
Mechanism. Hyperforin in St. John's wort activates the pregnane X receptor, inducing intestinal P-glycoprotein. Dabigatran etexilate is a P-gp substrate, and P-gp induction reduces its intestinal absorption. Studies with the model P-gp inducer rifampin show ~66% reduction in dabigatran AUC, and St. John's wort is expected to produce a similar effect.
Recommendation. Avoid St. John's wort entirely while taking dabigatran. If you have been taking both, do not stop the dabigatran but stop the St. John's wort and tell your prescriber so dabigatran levels and clinical response can be reassessed.
Sources (2)
- Nicolussi S, Drewe J, Butterweck V, Meyer Zu Schwabedissen HE. Clinical relevance of St. John's wort drug interactions revisited. Br J Pharmacol. 2020;177(6):1212-1226. PMID 31742659
- Härtter S, Sennewald R, Nehmiz G, Reilly P. Oral bioavailability of dabigatran etexilate (Pradaxa(®)) after co-medication with verapamil in healthy subjects. Br J Clin Pharmacol. 2013;75(4):1053-62. (DOAC P-gp mediated DDIs context.) PMID 22946890
Stack Score
How this pair moves the number.
Effect on the composite score
If both Dabigatran and St. John's Wort are in the same stack, this pair applies −10 to your Stack Score (per scored conflict row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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