Aim: To assess possible improvements in drug delivery to unresectable liver tumours we investigated the pharmacokinetics of intrahepatic doxorubicin in the dog liver with and without inflow occlusion.
Methods: Using a lattice template, doxorubicin was injected into 16 sites (over a 9 cm2 area) in each of three lobes of the liver for a total of 48 sites. The total doses of doxorubicin used were 4.8 mg and 96 mg (0.1 and 2 mg/site). Dogs with intravenous and intra-arterial delivery of the same total doses of doxorubicin were used as controls. Experiments using intrahepatic injection were performed with and without a 30 min occlusion of the hepatic artery, common bile duct and portal vein (inflow occlusion). The studies with vascular stasis were performed to determine if drug clearance from the injection sites and their plasma levels were reduced. Also, it was observed that blood and drug loss along the needle tract was reduced when inflow occlusion was used. Plasma and liver samples were harvested over a 90-min period and analysed by high pressure liquid chromatography (HPLC).
Results: In plasma mean peak levels and mean area under the curve (AUC) were significantly lower with intrahepatic doxorubicin (P<0.05) than with intravenous or intra-atrial delivery. In the liver AUCintrahepatic/AUCintravenous ratios were 3.45 and 3.6 with 4.8 mg and 96 mg of doxorubicin respectively. The AUCintrahepatic/AUCintraarterial ratios were 1.97 and 1.65 respectively. The liver extraction ratio (AUCliver/AUCplasma) after intravenous administration with 4.8 mg and 96 mg of doxorubicin was 31.9 with both doses of doxorubicin. The corresponding extraction ratios were 107.6 and 51 for intra-arterial administration and 425.2 and 237.7 for intrahepatic administration for the two doses of doxorubicin. Intrahepatic injection with inflow occlusion minimized the leakage back along the needle-tracts. The liver visibly retained the injected drug more completely. However, there was a decrease in systemic clearance resulting in a reduction of the pharmacological advantage.
Conclusion: These results indicate that lattice-intrahepatic administration of doxorubicin into the liver using a lattice template was associated with a significant increase in local and decrease in systemic exposure as compared to intravenous or intra-arterial administration of the same doses. Simultaneous occlusion of arterial and portal venous inflow was not shown to improve regional drug delivery. These pharmacokinetic studies may constitute a basis for palliative treatment of liver tumours by lattice intralesional injection when these cancers are found to be unresectable at the time of exploratory surgery.