Abstract: AimTo study the preparation of hydroxypropyl methylcellulose phthalate(HPMCP) nanoparticles and compare its pharmacokinetic characteristics with Neoral. MethodsHPMCP nanoparticles loaded cyclosporine A were prepared by solvent-nonsolvent method. CyA-HP50 nanoparticles, CyA-HP55 nanoparticles and Neoral were orally administered at the dosage of 15 mg·kg^-1 to rats. The CyA concentration in blood were determined by HPLC. Pharmacokinetic parameters were calculated by 3P97 program. ResultsThe concentration-time data of the three preparations were best fit by two compartment model. The relative bioavailability of CyA-HP50 and CyA-HP55 nanoparticles calculated by the AUC_0-72 were 82.3% and 119.6%, bioequivalent to the reference of Neoral. The relative bioavailability of CyA-HP55 nanoparticles was 145.3% of CyA-HP50 nanoparticles. Conclusion CyA HPMCP nanoparticles could be prepared easily and reproducibly. It was found that the oral absorption of CyA can be increased by using the HPMCP nanoparticles.