Dynamics of vitamin K antagonist and new oral anticoagulants use in atrial fibrillation: A Danish drug utilization study

Abstract

Background: Detailed data on real-life utilization of vitamin K antagonists (VKAs) and new oral anticoagulants (NOACs) in atrial fibrillation are sparse. Objectives: To describe the dynamics of VKA and NOAC use: that is, (i) how patients moved in and out of, as well as between, use of VKAs and NOACs; (ii) how patients adhered to treatment; and (iii) which type of prescriber initiated, maintained, and changed treatment with VKAs and NOACs. Methods: We conducted a drug utilization study in the region of southern Denmark (population 1.2 million) using prescription data. We included all subjects using VKAs or NOACs during the period of August 22, 2011, through June 30, 2013, restricted to subjects with a diagnosis of atrial fibrillation. Results: We identified 20 911 subjects, of whom 20 769 and 1639 used VKAs and NOACs, respectively. The number of VKA users was stable at ~ 14 000 subjects during the study period, whereas the number of NOAC users increased to 903. The majority of NOAC users had previously used VKAs (n = 974), whereas 389 anticoagulant-na€ive users initiated NOAC therapy. Among the latter, 51.2% had changed to VKAs within 6 months. 57.3% of VKA users were initiated by a hospital physician, whereas maintenance treatment was predominantly handled by the patient's general practitioner (97.6%). Switches from NOAC to VKA were initiated by a general practitioner in 69.2% of the cases. For users of NOACs, these numbers were 73.5%, 94.0%, and 63.3%. Conclusions: A large proportion of NOAC users switch to a VKA within a short time frame. The reasons for this are not clear.