Practice Pearl #1: International Society on Thrombosis and Haemostasis Statement

Paul Dobesh, PharmD, FCCP, BCPS, reviews the ISTH 2016 statement regarding the avoidance of DOACs in the obese population.

Jessica Kerr, PharmD, CDE: This brings us to, how do I apply what I need to do with the patient next? There’s been some confusion in how we use the DOACs in obesity. Obesity and anticoagulants have been the discussion on how we address that patient population. They have been around for a long time. I say a long time because I feel like I’ve been out of college for a long time. I remember during rounds, and this was a hot topic at that time when we were simply talking about low molecular weights and things. Dr Dobesh, share in discussion the position of the International Society on Thrombosis and Hemostasis [ISTH]. Share the position they have taken regarding DOACs in the obese population. What were the rationales for that decision?

Paul Dobesh, PharmD, FCCP, BCPS: It’s a great question, and a question I receive often in clinical services, and I’m sure Matt does as well. In 2016, the ISTH put out a guidance statement saying that they clearly, just like most other guideline recommendations, support the use of DOACs over that of warfarin, and then they gave this “except.” They recommend avoiding DOACs in patients who weigh over 120 kg or have a body mass index greater than 40 because of a lack of data. Now, I find this kind of odd. There is a lack of data with every drug in that patient group. Where is the wealth of information to dose antibiotics in patients who have body mass index over 40? Or antipsychotics or something like that? I find it a little interesting that that’s the case. The flip side is that with warfarin you can adjust the INR and give a little more drug. The INR tells you where you’re at and if you can keep it there. The concern here is that DOACs are fixed doses for whatever disease state, unless you have renal insufficiency. Basically, is it OK if I give X mg of a drug to someone who is 80 kg and I give that same dose to someone who is 140 kg? For lack of an eloquent way to put it, is that enough drug to cover the bigger patient? Is it going to cover? As you spread that drug out through more tissue, more blood and everything, is it enough? That’s the concern when you’re using a fixed dose of an anticoagulant. That’s the rationale.

The thought is that, all right, if you use the DOACs in these very heavy patients, the expectation was that there would be a lack of efficacy and that warfarin would perform better because you could titrate the INR. And once you have an INR, you know, the patient is anticoagulated. Because we don’t monitor DOACs, we won’t know that, and so that’s the concern. It’s not really about bleeding, right? The concern is really about can you maintain efficacy in these heavier patients using a standard dose of drug?

Jessica Kerr, PharmD, CDE: Within that guidance, what are the specific cutoffs for BMI and weight?

Paul Dobesh, PharmD, FCCP, BCPS: The cutoff for BMI is greater than 40. As Dr Johnson described, this is the morbidly obese. They also use the cutoff of 120 kg. Those are the cutoffs. If you’re over those, as they are recommend in the 2016 ISTH guidance statement, maybe avoid DOACs in those patients.