ORLANDO – A high fraction of U.S. patients with atrial fibrillation receive an inappropriately low dosage of an anticoagulant for stroke prevention, often in a misguided attempt to avoid potential bleeding complications.
When physicians “reduce the dose to prevent a bleed they increase the risk for an ischemic stroke,” Elaine M. Hylek, MD, said in a video interview during the annual International AF Symposium.
Recent data on actual anticoagulant dosages prescribed to U.S. patients with atrial fibrillation show that “an unexpectedly high proportion of prescriptions for apixaban (Eliquis), dabigatran (Pradaxa), and rivaroxaban (Xarelto) are given at lower doses,” Dr. Hylek noted at the meeting. The lower-dose formulations with U.S. marketing are only appropriate for patients on apixaban with at least two of the following: serum creatinine 1.5 mg/dL or higher, age 80 years or older, and weight 60 kg or less; patients on dabigatran with moderate renal impairment or treated with dronedarone or systemic ketoconazole; or patients on rivaroxaban with a creatinine clearance of 15-50 mL/min.
For example, in the pivotal trial for apixaban only 5% of atrial fibrillation patients qualified for the lower dosage, yet recent data have shown that, in actual U.S. practice roughly a quarter of patients were on this lower dosage, said Dr. Hylek, professor of medicine at Boston University and director of the thrombosis and anticoagulation service at Boston Medical Center (Curr Med Res Opin. 2016 July;32:1277-79). A second recent report showed that among U.S. patients with atrial fibrillation hospitalized for an ischemic stroke 84% had received inadequate anticoagulation with either subtherapeutic dosages of anticoagulant or no anticoagulant at all (JAMA. 2017 Mar 14;317:1057-67).
Another manifestation of the underprescribing problem are patients with atrial fibrillation treated with aspirin only, an approach proven ineffective for preventing ischemic strokes in these patients, Dr. Hylek said.
Dr. Hylek has been an advisor to or has received honoraria from Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, Doasense, Janssen, Medtronic, Pfizer, and Portola, and she has received research funding from Boehringer Ingelheim, Bristol-Myers Squibb, and Janssen.