Multivesicular liposomes for the sustained release of thymopentin: stability, pharmacokinetics and pharmacodynamics.

The objective of the present study was to investigate the storage stability of thymopentin multivesicular liposomes (TP5-MVLs) prepared with different emulsifiers, and to study the pharmacokinetics and pharmacodynamics of the produced TP5-MVLs in vivo. The stability studies of TP5-MVLs indicated that MVLs particles prepared with mixed emulsifiers (Myrj52:solutolHS15 = 2:3) were stable at the storage temperature of 4 +/- 2 degrees C within 3 months. In addition, FITC-TP5-loaded MVLs was prepared for pharmacokinetic studies that after subcutaneous administration, the fluorescence signal lasted for about 5 days in plasma demonstrating that the rate of drug release from MVLs was very slow. The pharmacodynamic studies indicated that the therapeutic efficacy of TP5-MVLs after subcutaneous administration once every four days was the same as free TP5 solution after intravenous or subcutaneous administration once daily. In conclusion, MVLs, which possessed great storage stability, can be utilized to reduce the administration frequency of TP5, and therefore, served as a promising sustained release delivery system for polypeptide.