these new anticoagulants have many potential advantages over warfarin. they are rapid activation, no food and drug interactions, rapid onset and no need for invasive blood monitoring. has proven effective for preventing thromboembolism in atrial fibrillation and thrombophlebitis following orthopedic surgery.  now being tested for anticoagulation for mechanical heart valves

I was disappointed with the results of this megatrial. First, the benefits are very modest and without reduction in embolic events. Statistical significance was only achieved by adding hemorrhagic stroke to primary endpoints and then double-counting it in safety data. One can say the drug is safer than warfarin. On the other hand, even though  therapeutic INR was achieved   62% of the time, 38% of the time it was not, and likely most of it was above 3 which may explain more hemorrhagic strokes. I would be interested to know what was average INR in those patients. 62% is probably comparable to clinical practice, but I would expect better results in tightly controlled trial patients with doctors, nurses, and research assistants on top of them. I don't think that patients in the trial would end up being prescribed interacting medications without researchers knowing about it, although it happens a lot in a real world. So I am not sure that it is a fair comparison. In addition, there are questions about quality of data from some centers, unimpressive results from Europe, and of course, possibly some bias. All in all, I was hoping for better results and a cleaner trial since I am definitely not a big fan of warfarin monopoly.

There is still potential for drug interactions via the p-glycoprotein with the new factor Xa inhibitors.  We have less experience with this method of interaction and don't routinely look for it, as we do with CYP450 interactions.  These new anticoagulants can be affected by other drugs but we are not looking for it and cannot use the INR to catch it.  This is a great concern to me.