Increased plasma conc w/ strong CYP3A inhibitors eg, ketoconazole, itraconazole, clarithromycin, indinavir, nefazodone, nelfinavir, ritonavir, saquinavir, telithromycin, voriconazole. Decreased plasma conc w/ strong CYP3A inducers eg, phenytoin, carbamazepine, rifampin, rifabutin, rifapentin, phenobarb. Risk of interaction w/ OATP1B1 substrates eg, statins, valsartan, repaglinide. May result in serious or fatal infections w/ administration of live or live-attenuated vaccines.