Hepatic drug clearance in children with leukemia: changes in clearance of model substrates during remission-induction therapy.

We administered a "cocktail" of three model substrates for hepatic processes: antipyrine for oxidation, lorazepam for glucuronidation, and indocyanine green for hepatic blood flow, to children with acute lymphocytic leukemia (ALL). The plasma clearance of these substrates was determined before and after remission-induction therapy in 14 children with ALL. We found an improvement in clearance of antipyrine (0.65 to 0.95 ml/min/kg; P less than 0.01) and lorazepam (0.93 to 1.20 ml/min/kg; P less than 0.05) in 12 of 14 patients, with a mean increase of 67% and 52%, respectively, from before to after remission. There was no significant difference in mean indocyanine green clearance from before to after induction (14.8 vs. 14.4 ml/min/kg). There were no significant differences in liver function test results (SGOT, prothrombin time, or serum bilirubin) from before to after induction. Plasma concentrations of albumin, alpha 1-acid glycoprotein, and apolipoprotein A changed by a mean of +11.1%, -38.2%, and +68.6%, respectively, from before to after remission. However, these changes did not account for the changes in total plasma clearance of lorazepam, because lorazepam free fraction did not change and lorazepam free clearance increased by a mean of 83%. Our hypothesis is that eradication of hepatic leukemic infiltration by ALL remission therapy resulted in an improvement in microsomal metabolism of antipyrine and lorazepam.