Oral anticoagulant dose often not reduced when kidney function drops

Contrary to guidelines, only about one in five patients with atrial fibrillation taking oral anticoagulants have their doses reduced when their kidney function declines, according to a new study.

"Even though Afib patients are on non-vitamin K oral anticoagulants (NOACs), they need to be followed up regularly for renal function, and NOACs dose should be adjusted accordingly," Dr. Taku Inohara of Duke Clinical Research Institute, in Durham, North Carolina, and Keio University School of Medicine, in Shinjuku-tu, Japan, told Reuters Health by email.

NOACs, commonly used for stroke prophylaxis in patients with atrial fibrillation (AF), are partially eliminated through the kidneys, and current U.S. and European guidelines recommend dose adjustment when renal function declines to avoid overanticoagulation. Whether this actually occurs in routine practice is unknown.

Dr. Inohara and colleagues used data from 6,682 patients in the ORBIT-AF II registry to evaluate changes in renal function in patients with AF over time and to determine whether NOACs have appropriate dose adjustments with kidney-function decline.

Overall, 23.1% of patients experienced worsening kidney failure, defined as a decrease of >20% in creatinine clearance from baseline at any time, during a median 361 days of follow-up.

Among the 4,120 patients who were on standard doses of NOACs at baseline, 154 (3.7%) met dose reduction criteria based on FDA dosing guidelines indicated on the package inserts.

Of these 154 patients, however, NOAC dosing was appropriately reduced in only 31 (20.1%), the researchers report in Heart.

Compared with patients whose NOAC doses were appropriately reduced, those without appropriate dose reduction had higher rates of major bleeding (1.7% vs. 0%) and bleeding hospitalization (2.6% vs. 0%) at one year.

The rate of later recovery of renal function did not differ between patients with appropriately reduced doses (24.1%) and those without (23.3%).

"Further evidence is warranted to see whether appropriate dose reduction based on routine serum creatinine monitoring improves patient clinical outcomes," the authors conclude.

Dr. Jason G. Andrade of the University of British Columbia, in Vancouver, Canada, recently found that some formulas commonly used to estimate glomerular filtration rate misclassified patients with respect to NOAC dosing. He told Reuters Health, "Clinicians need to be aware that the AF population is at risk of progressive renal dysfunction."

This means that "the longitudinal care of AF patients must include serial reassessment of renal function, with adjustment of the anticoagulation dose based on the results of these assessments in order to avoid adverse outcomes, such as bleeding," said Dr. Andrade, who was not involved in the new study.

Dr. Harpreet S. Bhatia of the University of California, San Diego, in La Jolla, and Weill Cornell Medicine, in New York, who recently found NOACs to be more effective than and as safe as warfarin in patients with AF and chronic kidney disease, told Reuters Health by email, "NOACs have quickly gained prominence and are now, as the study points out, recommended over warfarin for stroke prevention in atrial fibrillation in the AHA/ACC/HRS (American Heart Association/American College of Cardiology/Heart Rhythm Society) guidelines. However, each NOAC has a different degree of renal clearance, with different recommendations for dose reductions based on creatinine clearance." "Providers need to be aware of the recommendation to regularly monitor renal function and to be aware of renal function thresholds which should trigger evaluation for dose reductions," said Dr. Bhatia, who also was not involved in the study.

Janssen Scientific Affairs LLC sponsors the ORBIT AF registry but had no role in the design and conduct of this study.

SOURCE: https://bit.ly/2TIaBDb

Heart, online January 7, 2020.