The study in the journal Blood Advances pointed out that AF patients face a fivefold risk of stroke and often are prescribed anticoagulants to slow blood clotting. Physicians seeking to reduce the risk of unwanted and sometimes dangerous bleeding and other known adverse effects of DOACs might choose to prescribe lower dosages to patients deemed at high risk for bleeding.
“We found that 58% of bleeding complications occurred in patients who were treated with low doses of DOACs,” explained study coordinator Gualtiero Palareti, MD, of the Arianna Anticoagulation Foundation in Bologna, Italy. “Not only did the use of low doses not reduce bleeding risk, it also did not prevent patients from developing high blood levels of the medication.”
The researchers found a relationship between high baseline DOAC levels and early bleeding events in the 1-year follow-up and suggested that early measurement would allow the identification of patients with high DOAC levels and enable healthcare professionals to adjust treatment to reduce bleeding events.
For the “Measure and See” (MAS) study, venous blood was collected 15 to 30 days after DOAC initiation in AF patients who were followed for 1 year to record the occurrence of major and clinically relevant nonmajor bleeding. DOAC plasma levels were measured in one laboratory, and results were kept blind to patients and treating doctors.
The levels were assessed in 1,657 patients, with 57.7% receiving standard dosages and the remainder getting low dosages. The study team identified 50 bleeding events during follow-up. “Fifteen bleeding events (4.97% pt/yrs) occurred in patients with C-trough standardized values in the highest activity class (>0.50); whereas 35 events (2.69% pt/yrs) occurred in those with values in the two lower classes (≤0.50, P = 0.0401),” according to the report.
The authors pointed out that increasing DOAC levels and low-dose DOAC use were associated with increased bleeding risk in the first 3 months of treatment. Furthermore, the authors advised that 19% of patients receiving low dosages had standardized activity values in the highest class, adding that more bleeding occurred in patients treated with low- than standard-dose DOACs.
“Early measurement of DOAC levels in AF patients identified many subjects with high activity levels despite the low doses use and had more bleeding risk during the first 3 months of treatment,” the authors suggested.
Four DOACs are approved in the United States and Europe: apixaban, dabigatran, edoxaban, and rivaroxaban. DOACs are prescribed at fixed dosages based on a patient’s age, weight, and other health conditions.
In contrast to those on warfarin, most patients treated with DOACs do not undergo regular tests to measure blood levels of the medication. Recent studies have suggested, however, that blood levels of DOACs can vary considerably between patients and that levels that are too low or too high may increase the patients’ risk for blood clots and bleeding episodes.
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