SeriousConflict
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.
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.
SeriousCaution
Ginkgo biloba inhibits platelet-activating factor and platelet aggregation. Added to dabigatran's direct thrombin inhibition, the antiplatelet effect of ginkgo creates an additive bleeding risk, including spontaneous intracranial and ocular bleeding reported in case literature.
Recommendation: Avoid ginkgo biloba while taking dabigatran. If you have been combining them, stop the ginkgo and call your prescriber if you notice unusual bruising, nosebleeds, or any sign of bleeding.
ModerateCaution
Concentrated garlic supplements inhibit platelet aggregation. Added to dabigatran's direct thrombin inhibition, the antiplatelet effect can raise bleeding risk, particularly around surgery. Dietary garlic from cooking is not a concern.
Recommendation: Avoid concentrated garlic supplements (aged garlic, allicin capsules) while on dabigatran, and stop them at least 7 days before any planned surgery. Cooking with garlic is fine.
ModerateCaution
Fish oil's omega-3 fatty acids reduce platelet thromboxane A2 and can prolong bleeding time. Added to dabigatran's direct thrombin inhibition, high-dose fish oil (more than 3 g/day EPA+DHA) can additively raise bleeding risk.
Recommendation: Keep fish oil dose modest (≤2 g/day combined EPA+DHA) on dabigatran and keep the dose constant. Stop fish oil at least 7 days before any planned surgery and tell your prescriber if you notice unusual bruising or bleeding.
DangerousCaution
Nattokinase has fibrinolytic activity and can reduce clotting factors. Dabigatran directly inhibits thrombin, so combining the two may create additive anticoagulant and fibrinolytic effects. Major bleeding risk is especially concerning in older adults, kidney impairment, prior bleeding, or concurrent antiplatelet use.
Recommendation: Avoid nattokinase while taking dabigatran. If you have already combined them, stop nattokinase and contact your prescriber promptly if you notice unusual bruising, black stools, blood in urine, severe headache, or weakness.
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