Increased plasma conc w/ potent CYP3A4 inhibitors (eg, ketoconazole, posaconazole, voriconazole, PIs, clarithromycin, telithromycin); potent CYP2D6 inhibitors. Decreased plasma conc w/ CYP3A4 inducers (eg, phenytoin, carbamazepine, rifampicin, barbiturates or St. John's wort). Reduced plasma conc w/ substances that cause significant sustained elevation in gastric pH (eg, proton pump inhibitors, H2
-receptor antagonists, antacids). May alter plasma conc of CYP2D6 substrates w/ narrow therapeutic index. INR elevations &/or bleeding events w/ warfarin.