Arnica - Warfarin Interaction
Herbal: Arnica
Also Known As: American Arnica, Arctic Arnica, Arnica Flos, Arnica Flower, Arnikablüten, Bergwohlverleih, European Arnica, Foothill Arnica, Heart-Leaf Arnica, Hillside Arnica, Kraftwurz, Leopard's Bane, Mountain Arnica, Mountain Snuff, Mountain Tobacco, North American Meadow Arnica, Tw
Drug: Warfarin
Brand names:
Warfarin
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Apr 20, 2025
Interaction Details
Warfarin is classified as belonging to the following category: Anticoagulant/Antiplatelet Drugs
Theoretically, arnica might have additive effects with anticoagulant and antiplatelet drugs. Homeopathic arnica preparations are unlikely to have this interaction.
In vitro evidence shows that sesquiterpene lactones in arnica flowers can decrease platelet aggregation. However, this effect has not been reported in humans.
Interaction Rating
Likelihood of Occurrence
UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
References
- Schroder H, Losche W, Strobach H, et al. Helenalin and 11 alpha, 13-dihydrohelenalin, two constituents from Arnica montana L., inhibit human platelet function via thiol-dependent pathways. Thromb Res 1990;57:839-45.
Arnica Overview
Arnica is a plant that is native to Europe and North America and is part of the daisy family. It is known for its yellow, daisy-like flowers and has been traditionally used in homeopathic medicine to help decrease pain, swelling, and bruising. It has also been used in topical preparations to help reduce the pain from osteoarthritis. Arnica preparations are typically standardized according to the Homeopathic Pharmacopeia of the United States. In terms of drug interactions, it is important to note that in theory, arnica might have additive effects with anticoagulant and antiplatelet drugs but homeopathic arnica preparations are unlikely to have this interaction due to the extremely low amounts used.
Warfarin Overview
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Warfarin is used to prevent blood clots from forming or growing larger in your blood and blood vessels. It is prescribed for people with certain types of irregular heartbeat, people with prosthetic (replacement or mechanical) heart valves, and people who have suffered a heart attack. Warfarin is also used to treat or prevent venous thrombosis (swelling and blood clot in a vein) and pulmonary embolism (a blood clot in the lung). Warfarin is in a class of medications called anticoagulants ('blood thinners'). It works by decreasing the clotting ability of the blood.
Arnica - More Interactions
Arnica interacts with 120 drugs
Interaction Rating Key
These severity listings are for informational use only. Never start, stop or otherwise change your therapy before speaking with your provider.
| Major | The combined use of these agents is strongly discouraged as serious side effects or other negative outcomes could occur. |
| Moderate | Use cautiously under the care of a healthcare professional or avoid this combination. A significant interaction or negative outcome could occur. |
| Minor | Be aware that there is a chance of an interaction. Watch for warning signs of a potential interaction. |
| Unknown | No interactions have been reported or no interaction data is currently available. |
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Parts of this content are provided by the Therapeutic Research Center, LLC.
DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.
© 2021 Therapeutic Research Center, LLC
Drug descriptions are provided by MedlinePlus.
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Dr. Brian Staiger, PharmD
In addition to being a clinical pharmacist specializing in pharmacotherapy, Dr. Brian Staiger is a registered herbalist through the American Herbalist Guild. He has combined his passion for pharmacy practice with the study of medical ethnobotany to improve patient care. Feel free to reach out about any of your herbal or medication questions!
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