| Atorvastatin calcium belongs to BCA II class drugs,it has poor solubility and fast elimination in vivo,which result in its bioavailability of only about 12%.In order to increase the solubility of atorvastatin calcium,promote its in vivo absorpation and improve its bioavailability,atorvastatin calcium has been prepared to microemulision.However,due to its poor solubility in oil phase,directly make atorvastatin calcium into microemulision is not easy to achieve.In present study,we combined atorvastatin calcium and phospholipid to form phospholipid complexes,which could significantly improve the solubility of astorvastatin calcium in oil phase.With the method of preparing atorvastatin calcium and phospholipid complexes,we prepared the oral atorvastatin calcium submicron emulsion to improve its solubility in oil phase.In addition,we investigated its physicochemical property and storage stability to optimize its preparation process.Besides,the pharmacokinetic study indicated that atorvastatin calcium submicron emulsion could improve the bioavailability of atorvastatin calcium,and the small intestinal absorption experiments of rat showed that it could promote the absorption of drugs.Besides,Caco-2 cells were chosen to investigate the uptake mechanism of atorvastatin calcium submicron emulsion.Firstly,we investigated the preparation process of atorvastatin calcium submicron emulsion to screen out the best preparation process.The result showed when the molar ratio of atorvastatin calcium and phospholipid was 1:1,reacted 2 hours at 40? and the concentration of atorvastatin was 3 mg/ml,stable complexes could be prepared.The result also indicated that the solubility in oil phase and the oil and water partition coefficient of complexes could significantly improved.The result of FI-IR,DSC,XRD indicated that there is no chemical bond formation between drug and phospholipid,but through a certain interaction,to form a stable composite structure,during which the drug exists in the phospholipid with the amorphous state.We used atorvastatin calcium complexes as an intermediate to prepare oral atorvastatin calcium submicron emulsion.The final optimization of prescription was showed as follow: oil phase: 5% of soybean oil;aqueous lecithin: dosage was 1.4%,Twain 80 dosage was 0.8%,Bo Losham 188 dosage was 1%,0.05% of sodium oleate;the preparation process for the final optimization: the shear temperature was 70?,homogenization pressure was 1200 bar,homogeneous was 7 cycle times,homogenization temperature was 30?.The particle size of these three submicron emulsions prepared at the best prescription process was 120.8,123.3,and 121.8nm,the submicron emulsions we prepared were milky white,the viscosity was low,without wall hanging and the sterilization stability was good.According to the results of physicochemical properties of atorvastatin calcium submicron emulsion,we could make a conclusion,the appearance of the atorvastatin calcium submicron emulsion was milky white,and there was no wall hanging,its particle size was maintained at about 120 nm,and its final pH was pH6.5,and the encapsulation efficiency could reach to as much as 97.57%.The long-term stability result indicated that at 4?,atorvastatin calcium submicron emulsion remained stable within 6 months,during this time its size and pH changed little,maintain that in accordance with the stability of the prescription submicron emulsion prepared well.The results showed that the atorvastatin calcium submicron emulsion prepared in present study was stable.Compared with commercially available preparations,atorvastatin calcium submicron emulsion could prolong the drug release time of atorvastatin calcium in rats,and has obvious sustained release effect.The peak time of the commercially available formulation was 0.5 h,and the peak time of atorvastatin calcium phospholipid complex submicron was 0.75 h,which was slightly longer than that of the commercial preparation.The Cmax of the two groups was 0.531mg/L and 0.801mg/L respectively.The Cmax of the submicron emulsion group was 1.62 times higher than that of the commercial preparation group.The area under the curve(AUC)of the atorvastatin calcium micron emulsion group was 4.03mg/L·h,which was nearly 2.34 times higher than that of the commercial group(1.72mg/L·h),and its half-life was prolonged and the absorption rate constant increased too,indicated that atorvastatin calcium phospholipid submicron emulsion complexes could effectively promote the absorption of drugs in vivo,improve the body cycle time and significantly improve the bioavailability.The intestinal absorption experiment of rats showed that atorvastatin calcium phospholipid complex micron emulsion could significantly improve the atorvastatin calcium in the intestinal absorption,the absorption in colon was significantly improved,the absorption rate of each of the intestinal segments of atorvastatin calcium submicron emulsion was as follows: colon > duodenum > jejunum > ileum.The results are confirmed by the two indexes of absorption rate constant and apparent permeability coefficient.Finally,the uptake experiment of Caco-2 cell showed that cell uptake of micron emulsion was decreased to 71.3% when the energy inhibitor NaN3 was added,and the uptake of cell was reduced by 87.12% at 4?,these two points indicated that cell uptake of micron emulsion was a process of energy consumption.When chlorpromazine was used to specifically inhibite the ceft protein-mediated endocytosis,the micron emulsion uptake of cell was reduced by 64.28%,and when the lignin protein inhibitor was used to specifically inhibit cotyledonin-mediated endocytosis,cell uptake also decreased by nearly 38%,indicated that the uptake of micron emulsion of cells was related to these two channels.In addition,the change of cell membrane fluidity and intracellular pH can also lead to decreased cellular uptake of micron emulsion,but lattice-mediated endocytosis was likely to be the primary pathway for cellular uptake. |
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