Liver function, discontinue use if unexplained clinically relevant aminotransferase elevations occur, or if elevations are accompanied by increased bilirubin >2x ULN or by clinical symptoms of liver injury (eg, jaundice), obtain liver enzyme tests prior to initiation of treatment. Not to be initiated in patients w/ elevated aminotransferases (>3x ULN). Hb conc, not recommended in patients w/ severe anemia, measure Hb conc prior to initiation, after 1 mth & periodically thereafter. Pulmonary veno-occlusive disease. Concomitant use w/ strong CYP3A4 inducers & inhibitors. Concomitant use w/ moderate dual or combined CYP3A4 & CYP2C9 inhibitors. Renal impairment, not recommended in severe renal impairment. Childn & adolescents <18 yr. Elderly >75 yr.