The effect of cryoprotectants on the physical properties of large liposomes containing sodium diclofenac.

Large liposomes (1-10 microm) containing sodium diclofenac were prepared and lyophilized using lactose or mannitol (7.5% in respect to the lipid content) as cryoprotectants. The physical studies of liposomes were performed during 30 days of storage in a dry or resuspended form. Lyophilization of large liposomes and storage in the dry form at 5 degrees C increases their physical stability. Lactose is a cryoprotectant which does not influence changes of properties of liposomes regarding their size, encapsulation efficacy and release rate. Large liposomes lyophilized in the presence of mannitol tend to increase in size and encapsulation efficacy, but the lipid bilayers are stabilized and less permeable to the drug.