Drug Interaction Report

MONITOR CLOSELY: Use of oritavancin may interfere with the therapeutic monitoring of anticoagulants that depend on commonly used laboratory coagulation tests, as oritavancin can bind to and prevent the action of the tests' phospholipid reagents used to activate coagulation. Administration of oritavancin has been shown to artificially prolong the activated partial thromboplastin time (aPTT) for up to 120 hours and activated clotting time (ACT) for up to 24 hours following a single 1200 mg dose. Oritavancin my also artificially prolong the prothrombin time (PT) and international normalized ratio (INR) for up to 12 hours. However, studies indicate that oritavancin does not interfere with coagulation in vivo.

MANAGEMENT: For patients who require monitoring of anticoagulation within the indicated time after oritavancin dosing (e.g., aPTT less than or equal to 120 hrs, ACT less than or equal to 24 hrs, PT/INR less than or equal to 12 hrs), a non-phospholipid dependent coagulation test such as a Factor Xa (chromogenic) assay, or an alternative anticoagulant whose monitoring is not dependent on one of the affected tests may be considered.

ADJUST DOSING INTERVAL: Food reduces the oral bioavailability of betrixaban. When administered with a low-fat (900 calories; 20% fat) or high-fat (900 calories; 60% fat) meal, betrixaban peak plasma concentration (Cmax) and systemic exposure (AUC) decreased relative to administration in the fasting state by an average of 70% and 61%, respectively, with the low-fat meal and 50% and 48%, respectively, with the high-fat meal. The effect of food on betrixaban pharmacokinetics could be observed for up to 6 hours after meal intake.

MANAGEMENT: The manufacturer recommends taking betrixaban at the same time each day with food.