SPRAY-DRYING OF LIPOSOMES FOR A PULMONARY ADMINISTRATION .1. CHEMICAL-STABILITY OF PHOSPHOLIPIDS

Multilamellar vesicles constituted of soybean phosphatidylcholine (SPC ) and extruded through a 0.2 mum polycarbonate membrane were spray-dri ed in the presence of 10 % lactose. The particle mean diameter of the spray-dried product was about 7 mum when the liposomes were dispersed with a rotary atomizer. The dry residue can be resuspended in water to reconstitute liposomes without major change to the vesicle size distr ibution. Moreover, the chemical stability of the phospholipids was not significantly affected by this process, both in terms of hydrolysis a nd oxidation. It was concluded that spray-drying is a potentially inte resting means to produce stable dried liposomes that could be administ ered to the lung by inhalation.