Dong quai contains natural coumarins and has potentiated warfarin in a published case, raising bleeding risk.
What's happening
Dong quai (Angelica sinensis) root contains natural coumarin derivatives — ferulic acid, osthole, and related compounds — with documented antithrombotic and platelet-inhibitory activity in vitro. Because warfarin itself is structurally a coumarin, adding plant coumarins is mechanistically intuitive. Animal steady-state studies show dong quai significantly increases prothrombin time WITHOUT changing warfarin blood concentration — suggesting a pharmacodynamic rather than pharmacokinetic interaction. The primary human evidence is a single case report (Page & Lawrence 1999): a 46-year-old woman stable on warfarin self-initiated dong quai 565 mg 1-2 times daily. Over 4 weeks her INR rose to 4.05 then 4.90 — more than double baseline — without bleeding events. She stopped dong quai; INR returned to acceptable levels within a month. No other changes were identified. The washout pattern strengthens attribution, but a single case cannot establish population-level effect size. Two systematic reviews list dong quai among herbs with documented warfarin potentiation. Commercial dong quai preparations vary widely in coumarin content, so 'low dose' is hard to define reliably.
Recommendation
If you take warfarin, do not start dong quai without telling your prescriber. If you already take both, don't stop abruptly — ask for an INR check and a plan to discontinue. Watch for unusual bruising, gum bleeding, nosebleeds, or dark stools. For perimenopausal symptoms (the most common reason people take dong quai), discuss alternatives that do not interact with warfarin. Stop dong quai 1-2 weeks before elective surgery.
Timing
Spacing doses does not help; the interaction is pharmacodynamic and operates on the anticoagulation endpoint, not absorption.
Sources
— PMID:10417036 — Page RL, Lawrence JD. Potentiation of warfarin by dong quai. Pharmacotherapy 1999.
— DOI:10.1177/1934578X1400900835 — Warfarin Interactions with Medicinal Herbs. Natural Product Communications 2014.
— PMID:25707010 — Interaction between warfarin and Chinese herbal medicines. 2015.
How it works
Dong quai (Angelica sinensis) root contains natural coumarin derivatives — ferulic acid, osthole — with documented antithrombotic and platelet-inhibitory activity. Because warfarin itself is structurally a coumarin, adding plant coumarins is mechanistically intuitive. Animal steady-state studies show dong quai increases prothrombin time WITHOUT changing warfarin blood concentration — a pharmacodynamic rather than pharmacokinetic interaction.
Who should be careful
Warfarin patients, especially those using dong quai for perimenopausal symptoms (the main consumer-marketing use).
Any other anticoagulant or antiplatelet patient (aspirin, clopidogrel, DOACs) — same mechanism applies.
No RCT. Quantitative INR shift per dose of dong quai is unknown. Whether specific preparations (water extract vs ethanol tincture vs standardized capsule) differ in risk is unclear.
Why this severity
WARNING, not DANGER: evidence is a single case report + animal data + mechanism. Case had no bleeding and INR normalized on discontinuation. Not enough data for DANGER; not weak enough for CAUTION.
Evidence quality (GRADE): moderate
Frequently Asked Questions
Can I take dong quai and warfarin together?
Dong quai contains natural coumarins and has potentiated warfarin in a published case, raising bleeding risk.. If you take warfarin, do not start dong quai without telling your prescriber. If you already take both, don't stop abruptly — ask for an INR check and a plan to discontinue. Watch for unusual bruising, gum bleeding, nosebleeds, or dark stools. For perimenopausal symptoms (the most common reason people take dong quai), discuss alternatives that do not interact with warfarin. Stop dong quai 1-2 weeks before elective surgery.
How should I time dong quai and warfarin?
Spacing doses does not help; the interaction is pharmacodynamic and operates on the anticoagulation endpoint, not absorption.
Is this interaction dangerous?
This interaction is rated “Warning” by Formulate. Dong quai (Angelica sinensis) root contains natural coumarin derivatives — ferulic acid, osthole, and related compounds — with documented antithrombotic and platelet-inhibitory activity in vitro. Because warfarin itself is structurally a coumarin, adding plant coumarins is mechanistically intuitive. Animal steady-state studies show dong quai significantly increases prothrombin time WITHOUT changing warfarin blood concentration — suggesting a pharmacodynamic rather than pharmacokinetic interaction. The primary human evidence is a single case report (Page & Lawrence 1999): a 46-year-old woman stable on warfarin self-initiated dong quai 565 mg 1-2 times daily. Over 4 weeks her INR rose to 4.05 then 4.90 — more than double baseline — without bleeding events. She stopped dong quai; INR returned to acceptable levels within a month. No other changes were identified. The washout pattern strengthens attribution, but a single case cannot establish population-level effect size. Two systematic reviews list dong quai among herbs with documented warfarin potentiation. Commercial dong quai preparations vary widely in coumarin content, so 'low dose' is hard to define reliably.
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