Unchanged pharmacokinetics of etoposide given by intra-arterial hepatic infusion as compared with i.v. infusion

We investigated the pharmacokinetics of etoposide given to a patient suffering from multifocal liver metastases from an unknown primary tumor. The drug was given either by i.v. infusion or by hepatic arterial infusion (HAI). The calculated pharmacokinetic parameters (mean values +/- SD) were similar after i.v. infusion and HAI, viz., 6.4 +/- 0.7 versus 6.5 +/- 0.2 h for the terminal elimination half-life (t1/2 beta), 98.5 +/- 1.3 versus 101.3 +/- 5.9 mg l(-1) h for the area under the plasma concentration-time curve (AUC), 21.2 +/- 0.3 versus 20.6 +/- 1.2 ml min-1 m-2 for clearance (Cl), 17.7 +/- 1.9 versus 18.1 +/- 2.6 mg/l for the peak concentration, and 11.7 +/- 1.3 versus 11.6 +/- 1.01/m2 for the volume of distribution (Vd), respectively. We therefore conclude that administration of etoposide by HAI does not result in a significantly higher liver extraction. Hepatic extraction of etoposide is determined by the fraction of non-protein-bound (free) drug present. The lack of a difference between the two administration routes suggests that under in vivo conditions the equilibrium between free and bound drug is established before the drug reaches the hepatic arterioles. Consequently, administration by HAI does not lead to an increased exposure of the tumor in the liver to free (active) etoposide. Furthermore, the overall exposure of the liver to total (bound + free) etoposide is increased only from about 100 to 120 mg l-1 h. These results do not favor the use of this more complex route of drug administration in the treatment of (metastatic) cancer located in the liver.