Nonvalvular A-fib Patients More Likely to Remain on Dabigatran Than Warfarin

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Patients with nonvalvular atrial fibrillation (A-fib) on oral anticoagulation are more likely to persist in taking the direct thrombin inhibitor dabigatran than the vitamin K antagonist warfarin. Results from a large US administrative claims database were published online August 6, 2013, ahead of print in Circulation: Cardiovascular Quality and Outcomes.

Researchers led by Herman Sanchez, MBA, of Trinity Partners (Waltham, MA), used propensity scoring to evaluate 1,745 matched pairs of patients with newly diagnosed nonvalvular A-fib on oral anticoagulation with either warfarin or dabigatran between October 28, 2010, and June 30, 2012. Patients were identified from US Department of Defense claims data.

The researchers looked at patients’ persistence in taking their therapy, defined as the duration of time from initiation to discontinuation, stratified by 30- or 60-day gaps between prescription refills.

A Persistent Difference

Patients prescribed dabigatran had longer median persistence than patients prescribed warfarin whether taking into account a 30-day gap (389 days vs. 135 days; P < 0.001) or a 60-day gap (> 400 days vs. 222 days; P < 0.001). The persistence rates of patients prescribed dabigatran were higher than those of patients prescribed warfarin at 6, 9, and 12 months (table 1).

Table 1. Persistence in Propensity Score-Matched Patients

Persistence Rate

30-Day Medication Gap

60-Day Medication Gap

Dabigatran

Warfarin

Dabigatran

Warfarin

6 Months

63.9%

41.3%

71.8%

53.3%

9 Months

56.3%

30.7%

66.9%

44.0%

12 Months

50.3%

24.1%

63.3%

38.8%

P < 0.001 for all comparisons.

When assessed according to stroke risk, patients on dabigatran with a CHADS2 score less than 2 had lower 6- and 12-month persistence, respectively, than patients with a CHADS2 score greater than 2 analyzed with both a 30-day (62.1% vs. 65.9%; 47.3% vs. 52.0%) and 60-day (69.4% vs. 74.0%; 60.1% vs. 65.1%) medication gap.

The same trend was observed for patients prescribed warfarin analyzed with both a 30-day (36.9% vs. 43.0%; 20.2% vs. 25.3%) and 60-day (33.8% vs. 40.3%) medication gap.

Risk of Stroke, Bleeding Tied to Nonpersistence

On multivariable analysis looking at dabigatran patients with a 30-day mediation gap, factors associated with a greater likelihood of nonpersistence included:

  • Younger age (HR 0.99 for each year; 95% CI 0.98-1.00; P = 0.001)
  • Lower risk of stroke (HR 1.17; 95% CI 1.01-1.36; P = 0.032)
  • Greater risk of bleeding (HR 1.25; 95% CI 1.08-1.46; P = 0.003)
  • Higher comorbidity index (HR 1.04; 95% CI 1.01-1.07; P = 0.019)

For warfarin patients using a 30-day medication gap, factors associated with nonpersistence included:

  • Younger age (HR 0.99 for each year; 95% CI 0.98-0.99; P < 0.001)
  • History of intracerebral bleeding (HR 3.61; 95% CI 1.80-7.25; P < 0.001)

These factors were largely the same in each group when taking into account a 60-day medication gap. The only difference was that for patients on warfarin using a 60-day gap, patients residing in the Midwest (HR 0.56; 95% CI 0.40-0.79; P = 0.001) and the South (HR 0.81; 95% CI 0.68-0.96; P = 0.001) were less likely to be nonpersistent.

“Patients who initiated dabigatran treatment were more persistent than patients who began warfarin treatment,” the authors conclude. “Within each cohort, patients with lower stroke risk were more likely to discontinue therapy.”

The authors note that the bleeding risk that accompanies warfarin, as well as the frequent monitoring and drug-drug and drug-food interactions with the anticoagulant, often result in nonadherence and discontinuation. Dabigatran, meanwhile, has demonstrated superiority compared with warfarin in terms of stroke reduction without an increase in bleeding risk with the added benefit of not requiring INR monitoring.

Nevertheless, the current study was the first to compare persistence with therapy in those treated with either drug. Dabigatran was cleared for marketing in the United States by the US Food and Drug Administration on October 28, 2010.

Findings Reflect Clinical Experience

“These are very encouraging observations,” commented Gregory Y.H. Lip, MD, of the University of Birmingham (Birmingham, United Kingdom), in an e-mail communication with TCTMD. “My own clinical experience is broadly similar with better persistence with the novel oral anticoagulants. These drugs offer efficacy, safety, and convenience, and reflect the clinical practice shift recommended in guidelines such as those from the European Society of Cardiology.”

For instance, he explained, “Rather than focus on identifying ‘high-risk’ patients for warfarin, the initial decision step should be the identification of ‘low-risk’ patients (using the CHADS2-VASc score) who do not need any antithrombotic therapy. Subsequent to this initial step, patients with A-fib and ≥ 1 stroke risk factor can be offered effective stroke prevention, that is, oral anticoagulation—preferably with one of the novel oral anticoagulants.”

 

Source:

Zalesak M, Siu K, Francis K, et al. Higher persistence in newly diagnosed nonvalvular atrial fibrillation patients treated with dabigatran versus warfarin. Circ Cardiovasc Qual Outcomes. 2013;Epub ahead of print.

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Disclosures
  • The study was funded by Boehringer Ingelheim Pharmaceuticals.
  • Dr. Sanchez is an employee of Trinity Partners, which was contracted by Boehringer Ingelheim to work in collaboration on this study.
  • Dr. Lip reports serving as a consultant for Astellas, Bayer, Biotronik, Boehringer Ingelheim, Bristol-Meyers Squibb, Daiichi-Sankyo, Merck, Portola, and Sanofi Aventis, and on the speakers bureau for Bayer, Boehringer Ingelheim, Bristol-Meyers Squibb, Daiichi-Sankyo, Pfizer, and Sanofi Aventis.

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