5 Apixaban Apixaban was studied in two atrial fibrillation trials: AVEROES

and ARISTOTLE, both at 5 mg twice daily and 2.5 mg twice daily for patients at high risk of bleeding. In AVEROES, apixaban proved to be superior to aspirin monotherapy in reducing stroke and systemic embolism (1.6% per year vs. 3.7% per year, P <0.001). Major bleeding was Inhibitors,research,lifescience,medical similar between the two groups (1.4% per year vs. 1.2% per year, respectively; P=0.57).6 In ARISTOTLE, apixaban was proven superior to warfarin for stroke and systemic embolism (1.27% per year vs. 1.6% per year, P=0.01). Significant reductions in major bleeding was also seen in apixaban patients (2.13% per year vs. 3.09% per year, P=0.047).7 The cardiorenal advisory committee for the

FDA is to meet during Inhibitors,research,lifescience,medical the summer of 2012 to make recommendations for apixaban’s application. Clinical Considerations in Drug Use Renal Function Careful attention to renal function is necessary when considering any of the three new agents. All require dose reductions for impaired renal function and avoidance in end-stage renal disease and dialysis patients, whereas no such restrictions apply to warfarin. The minimum renal function, Inhibitors,research,lifescience,medical Dapagliflozin measured by CrCl, at enrollment in RE-LY and ROCKET-AF was 30 mL/min. However, the approved dosing for dabigatran allows a reduced dose for CrCl as low as 15 mL/min despite not having clinical outcomes from a randomized controlled trial.1, 3, 4 The ARISTOTLE trial allowed a serum creatinine level up to 2.5 Inhibitors,research,lifescience,medical mg/dL or a CrCl >25 mL/min for inclusion into the trial and reduced the dose to 2.5 mg daily when two of following criteria were met: age ≥80 years, weight <60 kg, or serum creatinine ≥1.5 mg/dL.7 Drug Interactions Drug interactions have plagued the patient on warfarin Inhibitors,research,lifescience,medical therapy. Currently, all oral anticoagulants have drug interactions with commonly used medications for rhythm or rate control of atrial fibrillation, although dose reductions for most of these drug interactions are not recommended with the new agents. Dabigatran is metabolized by ester hydrolysis with minimal conjugation and bypasses the Cytochrome P-450 (CYP-450)

system. It does compete with P-glycoprotein pathways, and therefore a dose reduction is recommended for patients with a CrCl between 30–50 Terminal deoxynucleotidyl transferase mL/min who are also taking dronedarone.3 Rivaroxaban and apixaban both are metabolized through the CYP-450 system. Specifically, rivaroxaban is metabolized by CYP 3A4, 3A5, and 2J2, and apixaban is metabolized by 3A4 and 3A5.5, 8 Specific dosing recommendations concerning drug interactions is minimal, and the current recommendation is to avoid concomitant therapy with metabolic inhibitors when possible due to increased risk for bleeding.5 There are no practical/proven anticoagulation assays to help direct dosage adjustment for any of the newer anticoagulants to account for these interactions.