Evaluation of dabigatran for appropriateness of use and bleeding events in a community hospital setting.

Oral anticoagulation has changed drastically in the past 4 years with the US Food and Drug Administration (FDA) approval of 3 new agents—dabigatran, rivaroxaban, and apixaban. Warfar-in has had a primary role in oral anticoagulation therapy for many decades. Although its efficacy and safety have been established, therapy with warfarin is associated with significant challenges, including the need for frequent monitoring, drug interactions, a delayed time to onset, and a narrow therapeutic index.1,2 The challenges associated with warfarin not only affect its efficacy, but they also impact patient satisfaction. These concerns have contributed to the development of novel oral anticoagulants, beginning with dabigatran etexilate. Dabigatran etexilate, a direct thrombin inhibitor, was approved by the FDA in October 2010 and is the first novel oral anticoagulant approved to reduce the risk for stroke in patients with nonvalvular atrial fibrillation (NVAF).3 Results from the Randomized Evaluation of Long-Term Anticoagulation Therapy (RE-LY) study demonstrated the superiority of dabigatran 150 mg orally twice daily compared with warfarin for the prevention of stroke and systemic embolism in patients with NVAF.4 In that study, the rate of major bleeding was similar between the agents; however, dabigatran demonstrated a lower risk for intracranial hemorrhage, but with an increased risk for major gastrointestinal (GI) bleeding, compared with warfarin.4 A recent analysis performed by the FDA confirmed these findings.5,6 In this analysis, compared with warfarin, dabigatran demonstrated lower rates of ischemic stroke, intracranial hemorrhage, and death; however, dabigatran was associated with a significant increase in major GI bleeding.5,6 In April 2014, dabigatran received new FDA indications for the treatment of patients with deep-vein thrombosis (DVT) and pulmonary embolism (PE) and for the risk reduction of recurrent DVT and PE in previously treated patients. Two studies, RE-COVER and RE-COVER II, compared dabigatran 150 mg twice daily with warfarin for the treatment of DVT and PE after 5 to 10 days of parenteral anticoagulation. Both studies demonstrated dabigatran's noninferiority to warfarin.7,8 When the RE-COVER study was initiated, dabigatran was the only agent approved by the FDA for the risk reduction of recurrent venous thromboembolism (VTE). In November 2011, rivaroxaban, a factor Xa inhibitor, was the second novel oral anticoagulant to receive FDA approval to reduce the risk for stroke in patients with NVAF.9 Results from the ROCKET AF trial demonstrated the noninferiority of rivaroxaban to warfarin for the first occurrence of stroke or systemic embolism.10 In November 2012, rivaroxaban received an additional indication for the treatment of and reduction in the risk for recurrent VTE. Two studies, EINSTEIN-DVT and EINSTEIN-PE, compared rivaroxaban (at an initial dose of 15 mg twice daily for 3 weeks, followed by 20 mg once daily) with enoxaparin 1 mg/kg twice daily for at least 5 days with warfarin and then continued with warfarin after the target international normalized ratio (INR) of 2.0 to 3.0 was reached.11,12 Both studies demonstrated the noninferiority of rivaroxaban to warfarin in time to first recurrent DVT or PE event.11,12 In December 2012, the factor Xa inhibitor apixaban was the newest novel oral anticoagulant to receive FDA approval to reduce the risk for stroke in patients with NVAF.13 The ARISTOTLE trial compared apixaban 5 mg twice daily (or 2.5 mg twice daily in select patients) with warfarin.14 Apixaban was superior to warfarin for the primary end point of reducing the risks for stroke and systemic embolism. Superiority to warfarin was primarily attributable to reductions in hemorrhagic stroke and ischemic stroke with hemorrhagic transformation compared with warfarin.14 In AVERROES, patients with NVAF who were not candidates for therapy with warfarin were randomized to treatment with apixaban 5 mg twice daily (or 2.5 mg twice daily in select patients) or to aspirin 81 mg to 324 mg once daily.15 The primary objective of the study was to determine if apixaban was superior to aspirin for preventing the outcomes of stroke or systemic embolism. This trial was stopped early on the basis of a prespecified interim analysis that showed significant reductions in stroke and systemic embolism with apixaban compared with aspirin, but apixaban was associated with a modest increase in major bleeding.15 KEY POINTS ▸ Anticoagulation has changed drastically in the past 4 years in the United States with the FDA approval of novel oral anticoagulants, starting with dabigatran in 2010, rivaroxaban in 2011, and apixaban in 2012. ▸ These new anticoagulants present a safe alternative to warfarin for the prevention of stroke and systemic embolism in the setting of nonvalvular atrial fibrillation (NVAF). ▸ However, although anticoagulation has been simplified with the novel oral drugs, many safety issues must be considered when prescribing these agents. ▸ This retrospective chart review at a community hospital analyzed the appropriateness use of dabigatran, the first novel anticoagulant to receive FDA approval for the treatment of NVAF. ▸ Of the 458 patients included in this study, 76 patients were prescribed an inappropriate, mostly too high, dose of dabigatran. ▸ Although dabigatran is only approved for the treatment of NVAF, 13 patients had valvular disease. ▸ The majority of the patients were also receiving concomitant medications that are known to have drug interactions with dabigatran. ▸ These results indicate that high-risk medications require better monitoring of prescribing habits to improve patient safety and outcomes. The current guidelines for the treatment of atrial fibrillation provide a class I recommendation for warfarin (level of evidence A) and dabigatran, rivaroxaban, and apixaban (level of evidence B) for the prevention of thromboembolism in patients with a CHA2DS2-VASc score of ≥2.16 Dabigatran provides an effective alternative therapy to warfarin. It offers a predictable pharmacokinetic profile, which eliminates the need for routine monitoring of serum drug concentrations. Approximately 80% of dabigatran is excreted renally and requires dose reductions for patients with reduced creatinine clearance.17 Although dabigatran addresses some of the challenges associated with warfarin, there are remaining issues regarding the use of dabigatran. Warfarin interacts with numerous medications, disease states, and a variety of foods containing vitamin K; however, there is a great deal of clinical experience and resources available to effectively manage many of warfarin's interactions.1 Unlike warfarin, dabigatran is not metabolized by cytochrome P450 enzymes and has fewer drug interactions. Although several drug interactions with dabigatran and P-glycoprotein inducers and inhibitors have been identified, little guidance has been provided on how to address them in practice.18 Additional concerns surrounding dabigatran include the lack of a reversal agent and the lack of availability of laboratory testing to determine its degree of anticoagulation activity. Dabigatran prolongs markers of coagulation, such as the activated partial thromboplastin time (aPTT) and ecarin clotting time, and may potentially impact INR values. The aPTT can only provide an approximation of the anticoagulation effect of dabigatran, and the INR is relatively insensitive to the degree of anticoagulation. The ecarin clotting time is a more specific parameter to determine the effect of anticoagulation19; however, most laboratories are not adequately equipped to perform the laboratory test. Without laboratory parameters to guide dosing adjustments, it is unclear how to balance the drug interactions that have been identified to potentially increase or decrease dabigatran serum concentrations. The lack of monitoring also makes it difficult to manage special populations that typically require dosage adjustments (eg, the elderly, obese patients, underweight patients, and those with renal dysfunction). Since dabigatran became the first oral anticoagulant to be introduced to the US market, and the first to be included on hospital formularies, there has been a dramatic shift in the approach to anticoagulation. Laboratory markers of anticoagulation effect are no longer reliable, drug interactions require significantly less dose adjustments, and renal function continually needs to be addressed.20 The purpose of this study was to evaluate the use of dabigatran at a community hospital between December 2010 and June 2012 and to identify prescribing areas that can be improved to ensure appropriate use and patient outcomes.