ABSTRACT
This chapter deals with the state of the art concerning the long term stability—shelf life—of pharmaceutical formulations of (phospho)lipid vesicles. The stability of the present and future liposomal products should preferably meet the standards of conventional pharmaceutical products: a shelf life of one year is considered to be an absolute minimum. Both chemical and physical stability aspects are involved. Several approaches have been developed to ensure the physical stability of lipid vesicles on storage; as mentioned above, high retention and prevention of aggregation or fusion over periods of many months are the major goals to achieve. Liposome dispersions with a narrow size distribution, that are freeze-dried in the presence of proper cryoprotectants, will form dispersions with a particle size distribution similar to that of the original liposome dispersion. Therefore this technique is preferred if small-size liposomes with a narrow size distribution are required.
