The short answer
Not known in people. In the lab, arjuna bark extract stopped platelets from clumping, which is how aspirin and clopidogrel prevent clots. The platelets came from 20 heart patients and 20 healthy people, but nobody swallowed arjuna. Other lab work found arjuna extracts block CYP2C9 and CYP3A4, liver enzymes the warfarin label names as handling warfarin.
We found no study of bleeding or INR in people taking arjuna with a blood thinner. If you take warfarin, acenocoumarol, aspirin or clopidogrel, tell your prescribing doctor before you start arjuna, and ask whether your INR should be checked and which bleeding signs to watch for.
Aspirin is sold in India as Ecosprin, warfarin as Warf, and acenocoumarol, a drug of the same family as warfarin, as Acitrom.
At a glance
| What was seen | How it may work | Direction | Evidence |
|---|---|---|---|
| Arjuna bark extract reduced platelet clumping in a dish[1] | Platelet inhibition (less calcium release and P-selectin on the platelet surface) | Could add to aspirin or clopidogrel; not tested in people | In vitro |
| Arjuna bark extracts blocked CYP2C9 and CYP3A4[2][4] | Enzyme inhibition in human liver microsomes | Could change warfarin levels; direction in people not known | In vitro |
No listing is not a clearance. A missing interaction here never means a combination is safe.
The evidence, study by study
Laboratory study on human platelets, 2009 In vitro
Platelets from 20 people with coronary artery disease and 20 matched healthy people were mixed with an ethanol extract of arjuna bark. Platelet clumping, calcium release and P-selectin, a marker of platelet activation, all fell. Nobody took arjuna by mouth, and the study did not measure bleeding. Lab findings like this show a possible route for an interaction. They do not show that one happens in people.[1]
Laboratory study, Mumbai, 2015 In vitro
Alcohol and water extracts of arjuna bark strongly blocked CYP3A4, CYP2D6 and CYP2C9 in human liver tissue in the lab. Three single compounds from arjuna did not. The authors predict drug interactions, but no warfarin levels or INR were measured.[2]
Long-term study in coronary artery disease, New Delhi, 2019 Observational
Thirty-five heart patients took arjuna bark extract (500 mg three times a day) with their usual medicines, which included aspirin, for nine months to almost five years. Another 35 took the usual medicines alone. Two people on arjuna reported gastritis and one constipation. The study was small, did not look at bleeding, and did not include a warfarin analysis.[3]
What your doctor may watch for
- INR, if you take warfarin or acenocoumarol. The warfarin label warns about botanical (herbal) products and about medicines that block CYP2C9, CYP1A2 or CYP3A4.[4]
- Unusual bruising or bleeding, such as bleeding gums, nosebleeds or black stools. INR does not measure the effect of aspirin or clopidogrel.
What to tell your prescribing doctor
You can read this out, or show them this page:
“I am taking, or planning to take, arjuna (name of product, form and how much) along with my blood thinner. Lab studies found arjuna slows platelet clumping and blocks enzymes that clear warfarin. Should my INR be checked, and which bleeding signs should I watch for?”
Withheld until review
Questions people ask
Does arjuna thin the blood?
In a lab dish, arjuna bark extract reduced platelet clumping in blood from heart patients and healthy people. Whether arjuna taken by mouth does the same, and whether it raises bleeding risk, has not been tested.[1]
Related
Arjunarishta
A fermented arjuna bark liquid used for the heart. It contains alcohol from fermentation, and the only study of it we found was in rats.
InteractionArjuna and blood pressure medicines
Arjuna capsules lowered blood pressure further in people taking telmisartan, in one small 28-day trial. Other BP drugs are untested.
InteractionArjuna and statins for cholesterol
In the lab, arjuna bark extract blocked CYP3A4, an enzyme that clears atorvastatin. Nobody has measured statin levels with arjuna.
InteractionAmla and blood thinners
Amla extract slowed platelet clumping in small human studies, alone and with aspirin or clopidogrel. Warfarin has not been tested.
Sources
- Malik N, Dhawan V, Bahl A, Kaul D. Inhibitory effects of Terminalia arjuna on platelet activation in vitro in healthy subjects and patients with coronary artery disease. Platelets. 2009;20(3):183-190. PMID 19437336.
- Varghese A, Savai J, Pandita N, Gaud R. In vitro modulatory effects of Terminalia arjuna, arjunic acid, arjunetin and arjungenin on CYP3A4, CYP2D6 and CYP2C9 enzyme activity in human liver microsomes. Toxicol Rep. 2015;2:806-816. PMID 28962416.
- Dwivedi S, Chopra D, Bhandari B. Role of Terminalia arjuna Wight and Arn. in the treatment of chronic coronary artery disease from pharmacovigilance point of view. AYU. 2019;40(2):104-108. PMID 32398910.
- Jantoven (warfarin sodium) tablets, US prescribing information (DailyMed).
Awaiting review by The Good Vaidya Medical Board. Prepared from the sources below and checked against each one.
Published 4 November 2026 · Last updated 4 November 2026
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