Show Notes
Jeff: Welcome back to EMplify the podcast corollary to EB Medicine’s Emergency medicine Practice. I’m Jeff Nusbaum and I’m back with Nachi Gupta. This month, we are tackling a topic for which the literature continues to rapidly change - we’re talking about the ED management of patients taking direct oral anticoagulants or DOACs, previously called novel oral anticoagulants or NOACs.
Nachi: Specifically, we’ll be focusing on the use of DOACs for the indications of stroke prevention in atrial fibrillation and the treatment and prevention of recurrent venous thromboembolisms.
Jeff: This month’s article was authored by Dr. Patrick Maher and Dr. Emily Taub of the Icahn School of Medicine at Mount Sinai, and it was peer reviewed by Dr. Dowin Boatright from Yale, Dr. Natalie Kreitzer from the University of Cincinnati, and Dr. Isaac Tawil from the University of New Mexico.
Nachi: In their quest to update the last Emergency Medicine Practice issue on this topic which was published in 2013, they reviewed over 200 articles from 2000 to present in addition to 5 systematic reviews in the cochrane database, as well as guidelines from the American Heart Association, European society of cardiology, and the american college of cardiology.
Jeff: Thanks to a strong literature base, Dr’s Maher and Taub found good quality evidence regarding safety and efficacy of the DOACs in relation to warfarin and the heparin-based anticoagulants.
Nachi: But do note that the literature directly comparing the DOACs is far more limited and mostly of poor quality.
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Jeff: Fair enough, we’ll take what we can get.
Nachi: Well, I’m sure more of those studies are still coming.
Jeff: Agree. Let’s get started with some basics. Not surprisingly, DOACs now account for a similar proportion of office visits for anticoagulant use as warfarin.
Nachi: With huge benefits including reduced need for monitoring and a potential for reduced bleeding complications, this certainly isn’t surprising.
Jeff: Though those benefits are not without challenges - most notably the lack of an effective reversal agent and the risk of unintentional overdose in patients with altered drug metabolism.
Nachi: Like all things in medicine, it’s about balancing and finding an acceptable risk/benefit profile.
Jeff: True. Let’s talk pathophysiology for a minute - the control of coagulation in the human body is a balance between hemorrhage and thrombosis, mediated by an extensive number of procoagulant and anticoagulant proteins.
Nachi: Before the development of the DOACs, vitamin K antagonists controlled the brunt of the market. As their name suggests, they work by inhibiting the action of vitamin K, and thus reducing the production of clotting factors 2, 7, 9, and 10, and the anticoagulant proteins C and S.
Jeff: Unfortunately, these agents have a narrow therapeutic window and many drug-drug interactions, and they require frequent monitoring - making them less desirable to many.
Nachi: However, in 2010, the FDA approved the first DOAC, a real game-changer. The DOACs currently on the market work by one of two mechanisms - direct thrombin inhibition or factor Xa inhibition.
Jeff: DOACs are currently approved for stroke prevention in nonvalvular afib, treatment of VTE, VTE prophylaxis, and reduction of major cardiovascular events in stable cardiovascular disease. Studies are underway to test their safety and efficacy in arterial and venous thromboembolism, prevention of embolic stroke in afib, ACS, cancer-associated thrombosis, upper extremity DVT, and mesenteric thrombosis.
Nachi: Direct thrombin inhibitors like Dabigatran, tradename Pradaxa, was the first FDA approved DOAC. It works by directly inhibiting thrombin, or factor IIa, which is a serine protease that converts soluble fibrinogen into fibrin for clot formation.
Jeff: Dabigatran comes in doses of 75 and 150 mg. The dose depends on your renal function, and, with a half-life of 12-15 hours, is taken twice daily. Note the drastic