Increased exposure & risk of dyspnea, bleeding, & other adverse events w/ strong CYP3A inhibitors (eg, ketoconazole, itraconazole, voriconazole, clarithromycin, nefazodone, ritonavir, saquinavir, nelfinavir, indinavir, atazanavir & telithromycin). Reduced exposure & decreased efficacy w/ strong CYP3A inducers (eg, rifampin, phenytoin, carbamazepine & phenobarb). Reduced effectiveness w/ aspirin maintenance doses >100 mg. Increased serum conc of simvastatin & lovastatin; avoid simvastatin & lovastatin >40 mg. Inhibits P-gp transporter; monitor digoxin levels w/ initiation of or change in therapy.