Abstract: AIMTo prepare the mitoxantrone long circulating liposomes (LCL) and to observe the residence behavior of the mitoxantrone LCL in rabbits. METHODSThe long circulating mitoxantrone liposomes were prepared by ethanol injection combined with the ammonium sulphate gradients method. Amphipathic polyethylene glycol-distearoyl phosphatidylethanolamine (PEG-DSPE) was added to modify the membrane of the liposomes. The column-switching system of RP-HPLC was utilized to determine mitoxantrone concentration in rabbit plasma. RESULTSThe mean diameter of the long circulating mitoxantrone liposomes was 60 nm, with the entrapping efficiency of 93.6%. With the same dosage (2 mg·kg^-1) iv in rabbits, the mean residence time (MRT) of the long circulating mitoxantrone liposomes was 9.8 h, while that of the normal liposomes was 3.6 h, and the AUC of the former is 6.4 fold greater than of the latter. It showed that the long circulating mitoxantrone liposomes prolonged the resident time of the drug in the blood circulating system and they reduced the uptake by the reticuloendothelial system, simultaneously. CONCLUSION Liposomes with high entrapping efficiency and small particle size could be prepared by ethanol injection combined with the ammonium sulphate gradients method, and the liposomes modified by PEG-DSPE could raise the AUC and prolonged the resident time of the drug in the blood circulating system.