title: Accelerated clearance of a second injection of PEGylated liposomes in mice.
abstract: We recently reported that the firstly injected PEGylated liposomes dramatically affected the rate of blood clearance of secondly injected PEGylated liposomes in rats in a time interval of injection dependent manner [J. Control. Release (2003)]. Mice are frequently used in evaluations of the therapeutic efficacy of PEGylated liposomal formulations, but the pharmacokinetics of repeatedly injected PEGylated liposomes in mice is not fully understood. In this study, therefore, we examined in mice the effect of the repeated injection of PEGylated liposomes on their pharmacokinetics. An intravenous pretreatment with PEGylated liposomes produced a striking change in the biodistribution of the second dose which was given several days after the first injection. The first dose resulted in a reduction in the circulation half-life of the second dose. The degree of alteration was dependent on the time interval between the injections. The rapid clearance of the second dose was strongly related to hepatic clearance (CLh). This finding suggests that a considerable increase in hepatic accumulation accounts for this phenomenon. But, no liver injury or an increase in the number of Kupffer cells were detected in histopathological evaluations. Collectively, although the multiple injections of the PEGylated liposomes had no obvious physical effects, such as inflammation, their pharmacokinetic behavior was clearly altered in mice. The results obtained here have important implications not only with respect to the design and engineering of liposomes for human use, but for evaluating the therapeutic efficacy of liposomal formulations in experimental animal models as well.
authors.affiliation: Department of Pharmacokinetics and Biopharmaceutics, Graduate School of Pharmaceutical Sciences, The University of Tokushima, 1-78-1, Sho-machi, Tokushima 770-8505, Japan. ishida@ph.tokushima-u.ac.jp
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Ishida
authors.forename: Kaori
authors.initials: K
authors.lastname: Masuda
authors.forename: Takako
authors.initials: T
authors.lastname: Ichikawa
authors.forename: Masako
authors.initials: M
authors.lastname: Ichihara
authors.forename: Kenji
authors.initials: K
authors.lastname: Irimura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kiwada
mesh_terms: D000818:Animals; D019540:Area Under Curve; D002626:Chemistry, Pharmaceutical; D002784:Cholesterol / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D007275:Injections, Intravenous; D008081:Liposomes; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D008657:Metabolic Clearance Rate; D051379:Mice; D010714:Phosphatidylethanolamines / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000633:toxicity; D010715:Phosphatidylglycerols / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000633:toxicity; D011092:Polyethylene Glycols / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000633:toxicity; D013154:Spleen / Q000187:drug effects / Q000378:metabolism; D014018:Tissue Distribution
chemical_list: D008081:Liposomes; D010714:Phosphatidylethanolamines; D010715:Phosphatidylglycerols; C038089:1,2-distearoylphosphatidylethanolamine; D011092:Polyethylene Glycols; C084352:distearoyl phosphatidylglycerol; C028210:monomethoxypolyethylene glycol; D002784:Cholesterol