|Posted by gulseth.michael on April 25, 2017 at 2:20 PM|
Soon after the advent of direct oral anticoagulation therapy, we were confronted with what should we do in patients with new or history of bariatric surgery. At our hospital, we quickly moved away from them in this population, but it is a deficient topic that in all of the DOAC package labels.
Thankfully, a recent, excellent review was pulblished on this topic:
Martin KA, Lee CR, Farrell TM, Moll S. Oral Anticoagulant Use After Bariatric Surgery: A Literature Review and Clinical Guidance. The American journal of medicine. May 2017;130(5):517-524.
I encourage all to read this, but here are the notations I took away from the article:
Changes to absorption of direct oral anticoagulants (DOACs, ie dabigatran etexilate [Pradaxa®], rivaroxaban [Xarelto®], apixaban [Eliquis®], and edoxaban [Savaysa®] likely affects the efficacy and safety of these medications in the bariatric surgery population.
The term “bariatric surgery” covers many different procedures such as adjustable gastric banding (AGB), sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), and biliopancreatic diversion with duodenal switch (PBD-DS).1 Different procedures likely have varying degrees of impact on DOAC efficacy and safety.
Bariatric surgery is theorized to potentially having the following effects on DOACs:
o Reduction of rivaroxaban absorption since it requires food for optimal absorption.
o Reduction in gastric acid production raising pH. Dabigatran is known to require an acidic environment for effective absorption.
o Motility may be increased leading to inadequate absorption.
o Surgeries that bypass the small intestine may alter enteric metabolism and efflux/influx of drugs across the intestinal wall.
o Disruption of drug absorption:
Apixaban is absorbed in the proximal small intestine, in addition to a little stomach absorption and colonic absorption.
Rivaroxaban is likely absorbed primarily in the stomach, with less absorption in the proximal small intestine.
Dabigatran is likely absorbed in lower stomach and proximal small intestine.
Edoxaban is mainly absorbed in the proximal small intestine
Patients who require bariatric surgery likely have much higher volumes of drug distribution than standard patients, and the volume of distribution can fluctuate as weight loss occurs. Some of the agents likely due distribute into the fats.
Although warfarin also relies heavily on gastric and proximal intestinal absorption, the dose can typically be customized to overcome any absorption issues by titrating to target INR, while the same is not true of DOAC agents since optimal target values are not known, and the difficulty in titration/laboratory testing.
My recommendations (which are very simiar to the article):
1. Clinicians should utilize warfarin therapy as the first line agent for patients who required systemic anticoagulation with a history of bariatric surgery. Further, patients on DOACs who have bariatric surgery should be converted to warfarin therapy in most cases.
2. If there is a compelling reason to utilize a DOAC over warfarin, I suggest considering the type of surgical procedure and pick an agent less likely to have absorption affected. (Apixaban appears to me to have the most optimal profile in that regard, but this is educated speculation on my part.) Further, I would suggest checking peak and trough levels to see if they are within the expected values. (If research drug levels are not available, could traditional labs be used? Difficult quesiton to answer. See http://members.webs.com/MembersB/editAppPage.jsp?app=blog&pageID=352382419#blog/show/44500337-doac-effects-on-traditional-labs)
Agree, disagree with my conclusions? Please comment below.