Investigation Of Pharmacokinetics For Liposomal HCPT Infused Through Hepatic Arteral Administration

ObjectiveThe first purpose of this study was to establish a high performance liquid chromatography with fluorescence detection method for the determination of hydroxycamptocecin in plasma and tissue of Japanese rabbits.The second purpose was to investigate the trends of drug concentration in plasma over time and pharmacokinetic parameters of HCPT solution and liposomal HCPT by being injected intravenously.The third purpose was to compare the concentration and duration in the central tumor and the peripheral tissue by using different methods of transcatheter arterial chemoembolization with HCPT solution and liposomal HCPT in rabbit VX2liver cancer model, and then choose the best way of transcatheter arterial administration.Methods1. High performance liquid chromatography with fluorescence detection method was used to analyze drug concentration in plasma and liver tissue. Excitation and emission wavelengths were360nm and380nm respectively. A Waters Symmetry C18analytical column (5μm,3.9×150mm) and a Shimadzu Wondasil C18guard column(5μm,4.O×10mm) were used; Mobile phase, ACN:0.15mM ammonium acetate buffer (pH6.5)=30:70(v/v); flow-rate, lml/min.2. Taking six Japanese rabbits, inject HCPT solution or liposomal HCPT through the marginal ear veins respectively. Get blood after administration of2,5,10,15,30,45,60,90,120,180,240minutes and detect the plasma drug concentration. Compartment model was fitted by the3P87pharmacokinetic calculation software. Compare the trends of drug concentration in plasma over time and pharmacokinetic parameters after injection of the two formulations in Japanese rabbits.3. Rabbit VX2liver cancer model was created. The conditions of transplantation ar growth of the tumors were checked by MRI scanning. These rabbits were randomized into four groups, fifteen of each. HCPT solution and liposomal HPCT were injected into hepatic arterial by using four different interventional methods as follows, group A:Liposomal HCPT+lipidol+polyvinyl alcohol(PVA); group B:Liposomal HCPT+PVA; group C: HCPT solution+lipidol+PVA; group D:HCPT solution+PVA. After administration of six hours, one day, three days, seven days and ten days, sacrificed these rabbits and detected HCPT concentration in the central tumor and the periphery liver tissue.Results1. The peaks of HCPT and the internal standard camptothecin (CPT) separated in Japanese rabbits’plasma and liver tissue. The endogenous substances did not interfere with the sample peaks. The emulsification time is2.4min for HCPT and4.8min for CPT. HCPT ranged a linear relationship in the concentration of0.2-20μg/ml and l-200ng/ml in plasma and liver tissue, the correlation coefficient R2of both were larger than0.999. HCPT recovery rate was between94.68%and103.60%in plasma and was between96.68%and117%in liver tissue. Variations during the days and within a day were less than10%either. The minimum detectable concentration was0.5ng/ml.2. HCPT solution and liposomal HCPT weighted the1/C/C three-compartment model. HCPT solution metabolic rate was fast after administration intravenously in the tested rabbits. The distribution half-life tl/2a was9.1348min, the elimination half-life t1/2βwas25.2492min, significantly lower than liposomal HCPT whose distribution half-life tl/2a was18.7772min and the elimination half-life tl/2βwas136.248min. And liposomal HCPT had bigger area under curve, lower clearance and less central compartment volume than HCPT solution.3. Drug concentration in the samples which were taken after infused through hepatic artery were detected after six hours, one day, three days, seven days and ten days. Concentration of HCPT decreased gradually in the central tumor and the peripheral tissue along with tb time.Fristly, comparing HCPT concentration of the same parts in the same time betwee groups. After6hours, concentration in the central tumor and the peripheral tissue of group A>group C>group D, group B>group O>group D (P<0.05). There was no significant difference among group A and group B; after one day, concentration of group D measured was less than the minimum detectable concentration, concentration in the central tumor and the periphearal tissue of group A>group C, group B>group C (P<0.05). There was no significant difference among group A and B; after three days, concentration of group D measured was less than the minimum detectable concentration, concentration in the central tumor and peripheral tissue of group A>group B>group C (P<0.05); after seven days, concentration of group C and group D measured were less than the minimum detectable concentration concentration, concentration in the central tumor and peripheral tissue of group A>group B (P<0.05); after ten days, concentration in all of the groups were less than0.5ng/ml.Then, compare HCPT concentration of different parts in the same time in the groups. After6hours, concentration in the central tumor were higher than which in the peripheral tissue in four of the groups, the differences of group B and group D were significant, and of group A and group C, were not significant. After one day and three days, concentration in the peripheral tissue in group A, B and C were higher than which in the central tumor, howerer, the differences of either was not significant. After seven days, concentration in the peripheral tissue in group A adn B were higher than which in the central tumor, the differences of both was not significant.Conclusion1. High performance liquid chromatography-fluorescence detection method which was used in this study can measure the drug concentration of HCPT in plasma and liver tissue. The results are reliable.2. Liposomal HCPT, compared with HCPT solution, both in plasma and in central tumor or in the peripheral liver tissue can play a more sustained release. So it can be maintained f(a longer time. 3. Transcatheter arterial chemoembolization of liposomal HCPT mixed lipiodol and PVA particles has the best effect to maintain drug concentration.