Better Prescribing Needed for Newer Atrial Fibrillation Agent

Prescribing methods for a newer atrial fibrillation agent require more monitoring to improve patient safety in community hospitals, according to a study published in American Health & Drug Benefits.

Anastasia L. Armbruster, PharmD, BCPS, assistant professor of pharmacy practice at the St Louis College of Pharmacy in Missouri, and her team of pharmacist researchers retrospectively analyzed 458 health charts from patients with nonvalvular atrial fibrillation (NVAF) who received at least 1 dose of the oral anticoagulant dabigatran between December 2010 and June 2012. Referencing FDA recommendations, the researchers assessed the appropriateness of each dabigatran prescription for stroke prophylaxis in NVAF.

“When utilized appropriately, dabigatran has demonstrated superiority over warfarin for the prevention of systemic stroke and embolism in the setting of NVAF without having to monitor serum drug concentrations,” the authors wrote. “However, with improved efficacy comes increased medication cost, various dosing regimens, and new challenges with maintaining safety in a hospital resulting from acute situations, such as changes in renal function, the initiation of novel medications, and the use of medical procedures.”

While the vast majority of those studied were prescribed dabigatran for the treatment of NVAF (93%), 3.9% were taking dabigatran for the treatment of venous thromboembolism (VTE), and 1.3% for pulmonary embolism. Since dabigatran had not yet been approved for the treatment or reduction of risk for recurrent VTE during the study’s duration, the authors classified this use as off-label. Additionally, 13 patients who received dabigatran had valvular disease, even though the anticoagulant is only approved for NVAF.

The pharmacist researchers categorized 76 patients (16.6%) as having an inappropriate dabigatran regimen, and 50 of them were taking too high of a dose based on their renal function. For 8% of the subjects, an inappropriate dabigatran prescription initiated at hospital admission continued at home. Even though 13 patients were receiving a once-daily dose of the anticoagulant, no FDA-approved dabigatran regimen includes such dosing.

In addition, many patients received medications that can interact with dabigatran. For instance, 204 patients (44.5%) received at least 1 P-glycoprotein inhibitor, and 13 patients (2.8%) received at least 1 P-glycoprotein inducer. A number of subjects also received concurrent antithrombotic therapy while taking dabigatran, and 1 or more doses of heparin or enoxaparin were concomitantly administered in 42.3% of them. Approximately 3 in 5 patients received daily aspirin, and 7.6% were taking what the pharmacists termed “triple therapy” comprised of aspirin, clopidogrel, and dabigatran.

“As the area of anticoagulation continues to evolve, it is imperative that hospitals institute monitoring systems to ensure the appropriate use of these high-risk medications,” the authors concluded. “Although methods are well-established for safely monitoring warfarin, newer agents also pose a safety risk to patients and thus require careful monitoring by competent clinicians.”