Trends in antithrombotic drug use and adherence to non-vitamin K oral anticoagulants in the Netherlands.

Susan Hanemaaijer,Annemieke Horikx,Martina Teichert,Fong Sodihardjo,Peter A G M De Smet,Michel Wensing,Marcel L Bouvy

doi:10.1007/s11096-015-0174-4

Abstract

Background Non-vitamin K oral anticoagulants (NOACs) became available in the Netherlands in 2008, providing another antithrombotic treatment besides vitamin K antagonists (VKAs) and antiplatelet agents (APAs). Objective To describe the patterns of antithrombotic drug use between 2008 and 2013 by examination of dispensing data form community pharmacies in the Netherlands; to determine the concomitant use of NOACs with VKAs and APAs and switching between the drug classes; and to compare adherence to NOACs with adherence to APAs. Setting An observational retrospective study was conducted using routinely collected dispensing data from Dutch community pharmacies. Methods For each calendar year, the numbers of NOAC, VKA, and APA users were calculated. Adherence was determined for NOACs and APAs by the percentage of days covered by medication (PDC). Information on the prescribed daily dose of VKAs was unavailable. Main outcome measures Comparison of age, sex, and co-medications of users of the three drug classes; concomitant use of different antithrombotic drug classes and switching between these in each year; and mean PDC and percentages of all users with a PDC above 80 %. Results NOAC use increased during the study period to 29,687 users in 2013. In that year there were 484,024 VKA users and 1313,032 APA users. Compared with users of VKAs, NOAC users were slightly younger and more frequently used antiarrhythmic drugs and beta blockers as co-medications. Substantial numbers of patients were dispensed potentially harmful combinations in 2013: 820 subjects were dispensed NOACs together with VKAs, and 684 subjects were dispensed NOACs, VKAs, and APAs concomitantly. Mean adherence to NOACs was 84.2 % compared with 87.3 % to APA. One in four NOAC users had a PDC lower than 80 % compared with one in five APA users. Conclusion Our findings show increasing use of NOACs by outpatients. The number of patients taking potentially harmful combinations of antithrombotic drugs was substantial. Adherence to NOACs in daily practice may be suboptimal to prevent thrombotic events.

Highlights

Vitamin K antagonists (VKA) have been used as anticoagulants for the past 70 years [1]
Adherence was determined for Non-vitamin K oral anticoagulants (NOACs) and antiplatelet agents (APAs) by the percentage of days covered by medication (PDC)
NOAC users made up 6 % of all users VKA users in 2013

Summary

Introduction

Vitamin K antagonists (VKA) have been used as anticoagulants for the past 70 years [1]. A recent meta-analysis in the United States showed that patients receiving warfarin for stroke prevention were within the therapeutic range only 55 % of the time [5] These disadvantages prompted the development of new oral anticoagulants with a rapid onset of therapeutic effect and fewer drug interactions [6, 7]. It is desirable that fixed doses can be used without the need for constant coagulation monitoring [1, 8,9,10,11] Among these new non-vitamin K oral anticoagulants (NOACs), dabigatran targets the coagulation enzyme thrombin, whereas rivaroxaban and apixaban inhibit factor Xa. In the Netherlands, dabigatran and rivaroxaban were licensed in 2008 for prophylaxis of venous thromboembolism in orthopaedic surgery for shortterm use up to 35 days after surgery [12, 13]. Setting An observational retrospective study was conducted using routinely collected dispensing data from Dutch community pharmacies

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