Drug Interaction Report

MONITOR CLOSELY: Coadministration of trastuzumab emtansine with anticoagulant or antiplatelet drugs may potentiate the risk of hemorrhagic events associated with these drugs. In clinical trials, fatal cases of hemorrhage occurred in patients receiving trastuzumab emtansine in addition to anticoagulant and antiplatelet therapy.

MANAGEMENT: Caution is recommended and additional monitoring should be considered if trastuzumab emtansine must be used with anticoagulant or antiplatelet drugs. In general, monitoring of platelet counts is recommended prior to each dose of trastuzumab emtansine. If platelet counts decrease to less than 50,000/mm3 (Grade 3 or higher), discontinue trastuzumab emtansine until platelet counts increase to 75,000/mm3 or higher (Grade 1 or less).

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of cilostazol. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. The extent and clinical significance are unknown. Moreover, pharmacokinetic alterations associated with interactions involving grapefruit juice are often subject to a high degree of interpatient variability.

MANAGEMENT: Until more information is available, the manufacturer recommends avoiding consumption of grapefruit juice during cilostazol therapy. Orange juice is not expected to interact with cilostazol.