Arnica slows the process of blood coagulation. Therefore, if taken with other anticoagulants or antiplatelet drugs, such as Warfarin, Hepadrin, Plavix or Coumadin, arnica can cause increased bleeding. Uses & Effectiveness? Possibly Effective for. Osteoarthritis. Early research shows that using an arnica gel product (A. Vogel Arnica Gel, Bioforce AG, Switzerland) twice daily for 3 weeks reduces. Does anyone take Arnica tablets whilst taking warfarin and aspirin? I was kicked by a horse last week in the leg and have lots of bruising and wondered if Arnica would help. 25 patient posts about Arnica and its potential interaction with Coumadin based on the insights of millions of patients and trusted online health resources. Many complementary medicines have confirmed or potential interactions with warfarin. These interactions can increase or decrease the anticoagulant effect of warfarin and have the potential to cause serious adverse events. According to Wikipedia: In a support group, members provide each other with various types of help, usually nonprofessional and non-material, for a particular shared, usually burdensome, characteristic. Osteoarthritis. Early research shows that using an arnica gel product (A. Vogel Arnica Gel, Bioforce AG, Switzerland) twice daily for 3 weeks reduces pain and stiffness and improves function in people with osteoarthritis in the hand or knee. Helpful, trusted answers from doctors: Dr. Waskowitz on does arnica gel interfere with blood thinners: Usually without problems! 83 patient posts about Arnica and its potential interaction with Warfarin based on the insights of millions of patients and trusted online health resources. You are taking warfarin or other blood thinners: Arnica may increase their effects. You are having surgery: In the lab, arnica has been shown to prevent the formation of clots. You have open cuts, wounds, broken skin: Arnica creams or ointments should not be applied to these areas.