Storage stability of stabilized MLV and REV liposomes containing sodium methotrexate (aqueous & lyophilized)

Multilamellar and unilamellar liposomes containing sodium methotrexate (MTX) were prepared by thin film hydration and reverse-phase evaporation methods. Encapsulation efficiency and release of MTX from liposomes at 4 degrees C, 25 degrees C and 37 degrees C were determined. When stored at 25 degrees C the liposomes lost 33% MTX after one month. To stabilize liposomes, they were freeze-dried in presence of different amounts of cryoprotectants (trehalose, PEG 10,000, PEG 20,000, and a mixture of trehalose-PEG 20,000). Measurements showed that the mixture of trehalose-PEG 20,000 imparted an MTX retention of about 70% after lyophilization. Stability tests of the lyophilized product at 4 degrees C, 25 degrees C and 37 degrees C demonstrated they were fairly stable even at 37 degrees C, indicating their potential use in commercial applications.