What are the challenges for the adoption of these newer, target-specific anticoagulants in the context of treating VTE (Figure 15)?  Certainly for most physicians there is a level of comfort with the widespread use of warfarin. [8] The principal issues with these new agents, therefore, are: 

•  cost and convenience: certainly the increased convenience is without question; the principal question therefore concerns the higher cost versus efficacy, with the latter about the same as with warfarin; 
  
  
• lack of an antidote: there are antidotes in development for the new agents and hopefully there will be specific antidotes within a year or so; 
  
  
• the wide therapeutic index means there is no need to monitor these agents, and this also means that there is not a test readily available to measure patient compliance;  
  
  
• which agent?  It is difficult to extrapolate from the randomized clinical trials to which drug might be better than the others, and given the enormous cost and complexity of head-to-head comparison trials, these are probably not going to be seen;
  
  
• it is often difficult to interpret the results of non-inferiority trials, particularly when the trial populations are different from the patients seen in clinical practice;
  
  
• finally, although many people, including the authors of the article referenced in Figure 15,[8] highlight potential problems with adherence with drugs requiring twice-daily administration, I would note that there are many drugs, particularly for diabetes, that are administered twice daily in clinical practice, and so that may not be so much of an issue.