| Nanoliposomes is a kind of nano-scale-lipsome drug-delivery system which displays unique advantages such as good biocompatibility?targeted?efficient,low toxicity and control release etc.After administration of nanoliposomes,there exists two forms in vivo:free drug and liposome-encapsulated drug,but only the free drug can bind the target and play efficacy.Traditional pharmacokinetic theories and methods can only quantitative or semi-quantitative analysis of the total drug concentrations in vivo and can't describe accurately the pharmacokinetic behaviors of nanoliposomes in vivo such as systemic exposure,biodistribution,release characteristics,metabolism and excretion process.Amphotericin B is a kind of macrocyclic lactones lactose polyene antibiotic which is extracted from the culture solution of streptomyces nodosus.Amphotericin B is considered to be the most effective antifungal agent and it exhibits wide-spectrum activity.However,its therapeutic use is hampered by its poor solubility and toxicity,particularly nephrotoxicity and neurotoxic,hematoxicity.To solve above problems,the Nexstar(US)company developed a nanoparticles liposomal formulation of amphotericin B(AmBisome,1990),AmBisome is a single bilayer drug delivery system which created by mixing specific proportions of amphophilic substances such as phospholipids and cholesterol so that they arrange themselves into multiple concentric bilayer membranes when hydrated in aqueous solutions,The liposome formulation improved the solubility of amphotericin B as well as its distribution in vivo,and it also reduced the toxicity of the drug.In this paper,we used AmBisome as test drug and developed a high-performance liquid chromatography-tandem mass spectrometry(LC-MS/MS)method to research on the pharmacokinetic behaviors of AmBisome in vivo.which provide new ideas and methods for the pharmacokinetic study of nanoparticles.Establish the analysis method of AmBisome in rat plasmaWe established a LC-MS/MS method to simultaneously quantify free amphotericin B and total amphotericin B in rat plasma.Firstly,we used protein precipitation methods which can completely destroy liposome with the full release of drug to quantitative analysis the total amphotericin B in rat plasma.Then,to determine the free amphotericin B concentration in plasma samples,we used solid phase extraction to separate the free amphotericin B from encapsulated amphotericin B because of the characteristics that solid phase extraction column can't adsorb liposomes.The results showed that the initial drug concentration of the total amphotericin B was 55.30 times higher than the concentration of the free drug in rat plasma.The area under the plasma concentration-time curve(AUC)of total amphotericin B was 13.5 folds higher than that of the free drug.It has been shown that all of the amphotericin B in plasma was mainly in the form of liposome-encapsulated.The lower concentration of free drugs in plasma reduces the acute hemolysis of amphotericin B.The half-life of free amphotericin B(t1/2)was 69.07 ± 31.04h,while the total amphotericin B ti/2 was 9.14 ± 1.36 h.According to above data,we can conclude that only quantitative of the total amphotericin B concentrations in vivo can't describe accurately the pharmacokinetic behaviors of AmBisome.Research on tissue distribution of AmBisome in rat.We used precipitating protein method to pretreat rat tissue sample and established a LC-MS/MS method for determination of amphotericin B in rat tissue.The results showed that compared with amphoterincin B,AmBisome could target to immune system.Because of AmBisome is a kind of nanoparticles-drug formulations,After administration of AmBisome,drug was mainly distributed in the liver,spleen,improving its antifungal activity.Meanwhile the concentration of drug in kidney was decreased.The nephrotoxicity of amphotericin B was highly correlated with the concentration of amphotericin B in kidney,so AmBisome had less renal toxicity compared with amphotericin B.The inhibition of AmBisome to human CYP450 enzymesThis paper used "cocktail”method in vitro.We developed a LC-MS/MS for determination of nine cytochrome P450 probe substrate metabolites.This method could studied on the inhibition of AmBisome and amphotericin B for CYP1A2,CYP2D6,CYP2E1,CYP2C9,CYP2C19,CYP3A4,CYP2A6 and CYP2B6.The results showed that amphotericin B could inhibit CYP2E1,and AmBisome had no inhibitory effect on eight kinds of CYP450 enzymes. |
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