| Objective: Irinorecan(CPT-11) is a synthetic derivative of the plant alkaloid camptothecin with increased aqueous solubility. It has passed clinical trials and is currently approved for the treatment of small cell lung cancer,cervical cancer,ovarian cancer,colonic and rectal cancer .Campto is irinotecan hydrochloride injection.However irinotecan is discovered to have serious side effects,such as neutropenia,thrombocytopenia,myelosuppression,gastrointestinal disorders (mainly diarrhea),liver and kidney dysfunction, and so on,which are recognized as constituting dose-limiting toxicity for this drug .Liposomes have been extensively used as drug carriers that can enhance the therapeutic activity of a number of drugs and reduce the serious side effects. Liposomes have the ability to passively accumulate in some tissues such as liver,spleen,lung.This process can result in the accumulation of significantly greater amounts of drug in some tissues than that can be achieved by the administration of free drug. Irinotean is selected as the sample drug.Methods: On the basis of preliminary experiments , determined irinotecan liposome preparation methods and then adopted the single factor prescription for the identification of factors affecting irinotecan liposome.The irinotecan liposome was prepared by film dispersion method,ether injection method and ammonium sulfate gradient method.The liposome and free drug were separated by using Sephadex G-50 column and then determined the entrapment efficiency(EE).Ammonium sulfate gradient method was selected to prepare liposomes.Orthogonal design was selected to optimize the formula of irinotecan liposome. Evaluation of the formulas was performed on the basis of the EE of the liposomes to select the optimal formula. The EE was taken as criterion to optimize the rate of lipid to cholesterol, the rate of drug to lipid, the concentration of ammonium sulfate, the incubation temperature and the incubation time. On this basis, four factors and three levels orthogonal design was employed to select the best formula. The range results finalized irinotecan liposome best formula.Respectively mapped irinotecan liposome and solution in vitro release curves, used of zero-order, first order, Higuchi and Weibull equation for fit, and calculation the coefficient correlation.Taking size of liposome, appearance, colour as indexs to inspect the physical and chemical stability of irinotecan liposome .A simple HPLC method with fluorescence detection was developed for the determination of irinotecan in rat plasma and mice tissue, Diamonsil C18 column (200×4.6 mm, 5μm) with the fluorescence detection set atλex 370nm andλem 530nm. The mobile phase was acetonitrile- citric acid (2.1% citric acid, pH was 3.8 setted by 30% natrium hydroxydatum, containing 0.2 % triethylamine) 40:60 v/v. Flow rate 1ml/min. The pharmacokinetic parameters were calculated by statistical moment program. The drug distribution of mice was investigation to evaluate targeting in tissues.Results: Ammonium sulfate gradient method of irinotecan liposomes preparation is efficient with higher EE. The optimal prescription is lipid 400mg, cholesterol 133mg, the concentration of ammonium sulfate is 0.2mol/L,the incubation temperature is 55℃. The entrapment efficiency was 90.7% ,the drug loding is 6.27% and pH was 6.20. The size of the resulting liposome was 215.7nm.The irinotecan release behavior from irinotecan solution in vitro was in accord with weibull equation and the equation was as follows: ln[-ln(1-Q)] = 0.8101lnt - 0.8293,r2=0.9934; The irinotecan release behavior from irinotecan liposome in vitro was in accord with zero-order equation and the equation was as follows: Q = 0.0077t + 0.0455,r2=0.9949. T50 and Td of irinotecan solution is 1.77h,2.78h , T50 and Td of irinotecan liposome is 59.03h,76.17h.The physical stability of irinotecan liposome was shown as follows: First,irinorecan liposome showed unstable under heating conditions; Second, it showed preferable stability under 4℃storage. The enterohepatic circulation (EHC) existed in pharmacokinetic behavior of both irinorecan and its liposome, the AUC of liposome was increased from 234.83μg·h·ml-1 to 539.25μg·h·ml-1, and the liposome k decreased from 0.3997h-1 to 0.2150h-1 .The biodistribution of irinotecan in mice tissues showed that liposome has the ability to passively accumulate in target tissues. The relative ingest rate in heart,spleen and lung of rats is3.13,4.76,2.56 respectivly. Liposome can accumulate greater amounts of drug in heart,spleen and lung than can be achieved by the administration of free drug .Conclusion: Ammonium sulfate gradient method for irinotecan liposome preparation is simple and efficient. The quality of liposome is controllable and it can remarkably enhances the medicine curative effect and reduces the side effects. The study enriched research content of irinotecan liposome. |
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