ABSTRACT
To prepare cyclosporine A (CyA) loaded block copolymer micelles and observe its release behaviors in vitro and pharmacokinetics in rats, methoxylpoly (ethylene glycol)-poly (D, L-lactide-co-glycolide) (mPEG-PLGA) was synthesized by ring-opening copolymerization of lactide and glycolide in the presence of methoxylpoly (ethylene glycol) (mPEG) as initiator. The structure of the mPEG-PLGA copolymer was confirmed with 1H NMR and FT-IR. The cyclosporine A loaded micelles (CyA-PM) were prepared by solvent evaporation method and their morphology was observed by the transmission electron microscope (TEM). The mean size and size distribution were determined by dynamic light scattering (DLS). The release behaviors in vitro and pharmacokinetics in rats were investigated by HPLC method using cyclosporine A injection commercial agent, sandimmune, as the reference. The obtained CyA-PM showed spherical shape with the core-shell structure, the mean particle sizes are in the range of 136.1-141.9 nm. The drug loading amount and entrapment efficiency were increased and the particle size became smaller with decreasing the ratio of acetone to water. With the increasing of the amount of cyclosporine A fed the drug loading increased, entrapment efficiency decreased and the particle size had no change. CyA-PM showed significant sustained release behave in vitro compared with sandimmune and only 9.7% of encapsulated cyclosporine A was released after 12 hours, the release characteristics was well fitted with Higuchi equation (r = 0.999). The Pharmacokinetics study at equal administration dosage (5 mg x kg(-1)) in rats showed the half-life (t1/2) of CyA-PM extended and the area under concentration-time curve (AUC) increased compared to sandimmune. The results also showed that cyclosporine A concentration-time data were all in accord with two compartment model. Cyclosporine A loaded mPEG-PLGA micelles showed obviously solubility enhancement, sustained release and overcome the side effect and toxicity of sandimmune resulted from solubiling agent-polyoxyethylene castor oil (Cremophor EL) and might be developed as a novel dosage form of cyclosporine A.
Subject(s)
Animals , Male , Rats , Area Under Curve , Cyclosporine , Pharmacokinetics , Delayed-Action Preparations , Drug Carriers , Pharmacokinetics , Drug Compounding , Half-Life , Immunosuppressive Agents , Pharmacokinetics , Micelles , Particle Size , Polyesters , Pharmacokinetics , Polyethylene Glycols , Pharmacokinetics , Polymers , Pharmacokinetics , Rats, Sprague-DawleyABSTRACT
To optimize the formulation and preparation method of multivesicular liposome of thymopentin and to investigate its pharmacokinetics in rats, the multivesicular liposome of thymopentin was prepared by double emulsification method and the formulation was optimized by orthogonal design. The release characteristics of thymopentin from multivesicular liposome in PBS (pH 7.4) and in plasma were investigated. The multivesicular liposome of thymopentin labeled with fluorescein isothiocyanate was prepared by double emulsification method. Its pharmacokinetics was evaluated following intramuscular injection in rats. The optimal formulation of multivesicular liposome of thymopentin were formulated with 7.5% glucose in aqueous phase and 2.25 mol x L(-1) triolein, 2.68 mol x L(-1) DPPG and 16.96 mol x L(-1) DOPC in organic phase. The entrapment efficiency of the multivesicular liposome of thymopentin was above 85% and the mean particle size was about 22 microm. The in vitro release of thymopentin from multivesicular liposome in PBS (pH 7.4) and in plasma was found to be in a sustained manner. The release curves were fitted to Higuchi equation. The pharmacokinetics following intramuscular injection of the multivesicular liposome of thymopentin labeled with fluorescein isothiocyanate in rats showed that the peak concentration of thymopentin was lower and elimination of it was slower significantly than that of thymopentin labeled with fluorescein isothiocyanate solution in the same dose. The plasma concentration of thymopentin maintained above quantitative limitation at 120 h after administration of multivesicular liposome of thymopentin. The optimized formulation and preparation technology of multivesicular liposome of thymopentin with higher entrapment efficiency are feasible with good reproducibility. Multivesicular liposome of thymopentin showed significant sustained-release property following intramuscular injection in rats.