4) Tidefelt U, Liliemark J, Gruber A, et al : P-Glycoprotein inhibitor valspodar (PSC 833) increases the intracellu- lar concentrations of daunorubicin in vivo in patients with P-glycoprotein-positive acute myeloid leukemia. J Clin Oncol 18 : 1837-1844, 2000