In Bhatt’s presentation (Bhatt, Figures 15, 16, 17, 18, 19) review the important information about therapy with the NOACs that have very recently become available or may be about to become available as potential substitutes for warfarin.  As discussed, these new agents appear to have many advantages over warfarin, but it is very important for physicians to be aware of how these new agents are different from warfarin. 

One of the most important differences, emphasized in the upper red highlight in Figure 16, is the rapid onset of the full anticoagulation effect (more or less 2 hours) of the new agents compared with warfarin (72–96 h).[12]  That is why for a patient who has had, for example, several polyps removed from the colon, it is medically acceptable to restart the warfarin the night after the procedure, whereas the new oral agents probably would not be restarted immediately after surgery because the full anticoagulation effect would be present within about 1–3 hours.  It is very important to prevent bleeding related to procedures, of course, and so a delay in restarting anticoagulation is a huge departure from warfarin.

In addition, the biologic half-life of the NOACs is also very different from warfarin’s.  Warfarin’s half-life is shown in the Figure as 40 hours, although in reality for an octogenarian patient the half-life of warfarin is probably closer to 50–60 hours.  This is very different from the half-lives of dabigatran, rivaroxaban, apixaban, and edoxaban, which have half-lives of between 10 and 14 hours.

Finally it is certainly also very important to remember the patient’s renal function.  As illustrated in the Figure, dabigatran is the agent that relies the most on the kidney for elimination, about 80%; rivaroxaban is about 33% excreted through the kidneys; for apixaban this is 25% and for edoxaban it is closer to 50%.  This is another of the nuances and differences that physicians need to be aware of when prescribing anticoagulation, as will be discussed in the Roundtable Discussion.