Metabolism and excretion of etoposide in isolated, perfused rat liver models

The clearance of etoposide and formation of etoposide glucuronide have been measured in an isolated, perfused rat liver model to evaluate the effect of impaired hepatic function on etoposide kinetics. Hepatocellular injury was produced by pretreatment of rats with allyl alcohol or carbon tetrachloride; ligation of the bile duct simulated obstructive biliary disease. Etoposide clearance (3.59 +/- 1.06 ml/min) was reduced by both carbon tetrachloride (2.07 +/- 0.64 ml/min; P = 0.05) and allyl alcohol treatment (2.14 +/- 0.62 ml/min; P = 0.05). Biliary obstruction also impaired etoposide clearance but to a lesser extent than hepatocellular injury (2.47 +/- 0.69 ml/min; P = 0.20 versus control). In both hepatocellular and obstructive models, direct biliary etoposide excretion decreased. The metabolic clearance of etoposide to its glucuronide declined by 36% in the hepatotoxin models but was not decreased by biliary obstruction. Following hepatic injury, there is a reduction in the metabolism and excretion of etoposide by the liver. This effect is most marked on biliary drug excretion. Obstructive biliary disease does not significantly alter etoposide glucuronidation. Since most cancer patients have increased bilirubin on the basis of obstructive disease, little or no etoposide dose alteration will be needed. However, in the patient with significant hepatocellular injury, impaired etoposide clearance will be more pronounced, and etoposide dose alterations may be needed.