Can Aspirin Eventually Replace Warfarin?

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October 31, 2014

by Kristin Lessig, PharmD Candidate

For patients that have experienced serious trauma, surgical procedures, long periods of bed rest, or have taken certain oral forms of birth control, there is an increased risk for a condition known as deep vein thrombosis (DVT).  Deep vein thrombosis (DVT) is a blood clot that most commonly forms within the deep veins of the legs. This clot can become dislodged from the vein and eventually make its way into the lung where it can become stuck in a pulmonary artery and result in serious complications. 1

One of the primary treatments for DVT is to prescribe a medication that acts as a blood thinner so that the blood cannot form clots that block the blood vessels. These types of medications are known as anticoagulants, with one of the most commonly used anticoagulants being a medication known as warfarin. This medication works by blocking the mechanism that initiates blood clotting. 1 However, warfarin tends to interact with many different medications, and warfarin also tends to make the blood so thin that it is difficult to stop any internal or external bleeding. 1, 2

U.S. News recently published a report discussing the possibility of using over-the-counter aspirin to help treat DVT.3 The news report stated that many patients who take warfarin generally take the medication long enough for the blood clot to be destroyed and then as a preventative measure to keep another clot from forming. 3 Most patients only take warfarin for approximately 6 months because while taking warfarin, it is necessary to have frequent doctor appointments and blood tests to determine if a change in dose is needed. Since many patients do not wish to continue taking warfarin for extended periods of time, physicians need to utilize some other form of treatment that will bring about better results and be easier for the patient to follow.

Recent studies have revealed that aspirin may actually be an efficient treatment for DVT since aspirin also works to thin the blood like warfarin does. Aspirin acts as a blood thinner by blocking the production of certain enzymes that cause blood platelets to clot together. 4 Prospective studies and randomized control trials have been performed in order to determine if aspirin was able to prevent the formation of another blood clot in patients who had previously suffered from DVT. In addition, these studies observed the effects of 100mg aspirin versus a placebo on myocardial infarction (heart attack), stroke, major bleeding, and cardiovascular death. 3, 5 As a result of these studies, it was shown that aspirin was more effective than the placebo at decreasing the risk of DVT by approximately 42%. 4,5 It is very important to realize, however, that these studies showed a serious limitation because they did not show the effects of treatment of DVT with aspirin alone. Instead, the studies focused on the effects of aspirin on DVT after the patient had already taken a much stronger anticoagulant medication. Therefore, it is necessary for a patient who has been diagnosed with DVT to seek a doctor’s approval before beginning self-treatment with aspirin. While these studies have shown that aspirin is capable of blood-thinning properties and can significantly decrease the risk of DVT recurrence, aspirin is not as strong as warfarin or other anticoagulant medications. 5

Based on the evidence from the studies, it is easy to see that a new and potentially more patient-friendly treatment for DVT is evolving. Using over-the-counter aspirin as a blood-thinner to prevent another blood clot from forming is potentially a safer option since the patient won’t experience as many drug interactions as they would if they were on warfarin. Also, taking aspirin instead of warfarin can be easier and more cost effective for the patient. The patient would not have to go to the physician as often for testing and dose changes, therefore giving the patient a more consistent treatment as well as cutting down on medical costs. If an individual has previously suffered from a DVT, I would highly recommend meeting with the physician to discuss the option of possibly using aspirin as a precaution against a second DVT.

Do you think it is wise for people to self-treat a fairly serious condition with over-the-counter aspirin instead of seeing their physician frequently?



  1. Obalum DC, Giwa SO, Adekoya-Cole T, Ogo CN, Enweluzo GO. Deep vein thrombosis: Risk factors and prevention in surgical patients. West Afr J Med. 2009; 28(2):77-82.
  1. Aspirin’s role in preventing recurring deep vein blood clots. Mayo Clin Health Lett. 2013; 31(5):4-4.
  1. Reinberg, S. Study: Aspirin Might Work Instead of Warfarin for Deep Vein Clots. U.S. News Website. Published August 26, 2014. Accessed October 4, 2014.
  1. Cossetto DJ, Goudar A, Parkinson K. Safety of peri-operative low-dose aspirin as a part of multimodal venous thromboembolic prophylaxis for total knee and hip arthroplasty. J Orthop Surg (Hong Kong). 2012; 20(3):341-343.
  1. Simes J, Becattini C, Agnelli G, et al. Aspirin for the prevention of recurrent venous thromboembolism: The INSPIRE collaboration. Circulation. 2014; 130(13):1062-1071.


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