Pulmonary distribution and clearance of two beclomethasone liposome formulations in healthy volunteers

The pulmonary distribution and clearance of Tc-99m-labelled beclomethasone dipropionate (Bec) dilauroylphosphatidylcholine (DLPC) and dipalmitoylphosp hatidylcholine (DPPC) liposomes were compared in 11 healthy volunteers usin g gamma scintigraphy. As delivered by using the Aerotech jet nebulizer both liposome aerosols had a suitable droplet size (mass median aerodynamic dia meter 1.3 mu m) allowing deep pulmonary deposition. However, in the total d rug output during the inhalation there was a relatively large difference be tween DLPC and DPPC of 11.4 and 3.1 mu g, respectively. In a gamma camera s tudy no significant differences existed in the central/peripheral lung depo sition between the DLPC and DPPC formulations. Progressive clearance of bot h Tc-labelled Bec liposomes was seen: 24 h after inhalation, 79% of the ori ginally deposited radioactivity of DLPC liposomes and 83% of that of DPPC l iposomes remained in the lungs. Thus there was slightly slower clearance of inhaled liposomes using DPPC instead of DLPC. We conclude that both liposo me formulations are suitable for nebulization, although aerosol clouds were more efficiently made from the DLPC liposome suspension. Our results suppo rt the view that liposome encapsulation of a drug can offer sustained relea se and drug action in the lower airways. (C) 1999 Elsevier Science B.V. All rights reserved.