The use, misuse and abuse of dabigatran

Comparative effectiveness and safety of low-strength and high-strength direct oral anticoagulants compared with warfarin: a sequential cohort study

OBJECTIVES

The aim of this study was to compare effectiveness and safety of low-strength and high-strength direct oral anticoagulants (DOACs) with warfarin in the Australian Veteran population.

DESIGN

Sequential cohort study using inverse probability of treatment weighting (IPTW) and propensity score matching. Initiators of high-strength (apixaban 5 mg, dabigatran 150 mg, rivaroxaban 20 mg) and low-strength DOACS (apixaban 2.5 mg, dabigatran 110 mg, rivaroxaban 15 mg) were compared with warfarin initiators.

SETTING

Australian Government Department of Veterans' Affairs claims database.

PARTICIPANTS

4836 patients who initiated oral anticoagulants (45.8%, 26.0% and 28.2% on low-strength, high-strength DOACs and warfarin, respectively) between August 2013 and March 2015. Mean age was 85, 75 and 83 years for low-strength, high-strength DOACs and warfarin initiators, respectively.

MAIN OUTCOME MEASURES

One-year risk of hospitalisation for ischaemic stroke, any bleeding event or haemorrhagic stroke. Secondary outcomes were 1-year risk of hospitalisation for myocardial infarction and death.

RESULTS

Using the IPTW method, no difference in risk of ischaemic stroke or bleeding was found with low-strength DOACs compared with warfarin. As a class, no increased risk of myocardial infarction was found for low-strength DOACs, however, risk was elevated for apixaban (HR 2.25, 95% CI 1.23 to 4.13). For high-strength DOACs, no difference was found for ischaemic stroke compared with warfarin, however, there was a significant reduction in risk of bleeding events (HR 0.63, 95% CI 0.44 to 0.89) and death (HR 0.40, 95% CI 0.28 to 0.58). Propensity score matching showed no difference in risk of ischaemic stroke or bleeding.

CONCLUSION

We found that in the practice setting both DOAC formulations were similar to warfarin with regard to effectiveness and had no increased risk of bleeding.

Optimizing Stroke Prevention in Patients With Atrial Fibrillation: A Cluster-Randomized Controlled Trial of a Computerized Antithrombotic Risk Assessment Tool in Australian General Practice, 2012-2013

INTRODUCTION

Clinicians have expressed a need for tools to assist in selecting treatments for stroke prevention in patients with atrial fibrillation. The objective of this study was to evaluate the impact of a computerized antithrombotic risk assessment tool (CARAT) on general practitioners' prescribing of antithrombotics for patients with atrial fibrillation.

METHODS

A prospective, cluster-randomized controlled trial was conducted in 4 regions (in rural and urban settings) of general practice in New South Wales, Australia (January 2012-June 2013). General practitioner practices were assigned to an intervention arm (CARAT) or control arm (usual care). Antithrombotic therapy prescribing was assessed before and after application of CARAT.

RESULTS

Overall, the antithrombotic therapies for 393 patients were reviewed by 48 general practitioners; we found no significant baseline differences in use of antithrombotics between the control arm and intervention arm. Compared with control patients, intervention patients (n = 206) were 3.1 times more likely to be recommended warfarin therapy (over any other treatment option; P < .001) and 2.8 times more likely to be recommended any anticoagulant (in preference to antiplatelet; P = .02). General practitioners agreed with most (75.2%) CARAT recommendations; CARAT recommended that 75 (36.4%) patients change therapy. After application of CARAT, the proportion of patients receiving any antithrombotic therapy was unchanged from baseline (99.0%); however, anticoagulant use increased slightly (from 89.3% to 92.2%), and antiplatelet use decreased (from 9.7% to 6.8%).

CONCLUSION

Tools such as CARAT can assist clinicians in selecting antithrombotic therapies, particularly in upgrading patients from antiplatelets to anticoagulants. However, the introduction of novel oral anticoagulants has complicated the decision-making process, and tools must evolve to weigh the risks and benefits of these new therapy options.

Adherence and outcomes of patients prescribed dabigatran (Pradaxa) in routine clinical practice

AIM

To explore and detail clinical experiences of dabigatran, a novel anticoagulant, after it became available in New Zealand in July 2011.

METHODS

A cohort of patients was recruited from Hutt Hospital and the two largest primary care practices in the Hutt Valley region. They were included if they took at least one dose of dabigatran between July 2011 and April 2012. Participants undertook a questionnaire 3-12 months after starting dabigatran assessing adherence, perceived side-effects and complications. Those presenting due to an adverse event were analysed separately.

RESULTS

Of 102 patients identified, 92 were recruited to this study. At a median of 8 months, 70% of participants were still taking dabigatran, significantly lower than in the RE-LY trial at 12 months (P = 0.0002). The commonest reason given for discontinuation was gastrointestinal (GI) side-effects. Rates of serious adverse outcomes on dabigatran therapy were relatively low. Patients expressed polarised comments, both positive and negative, regarding their experiences of dabigatran.

CONCLUSIONS

A high rate of discontinuation of dabigatran, mainly due to GI symptoms, was observed. There does not appear to be any specific predictor of dabigatran tolerance. When prescribed according to guidelines, rates of serious adverse events associated with dabigatran appear to be low.