Comparison of jet and ultrasonic nebulizers for alveolar targeting of methylprednisolone

The secondary systemic effects of oral corticosteroid therapy in chronic lung disease indicate the possible benefits of local therapy. The aim of this study was to show if alveolar targeting of a corticosteroid, methylprednisolone (MP), is possible, and to determine which type of nebulizer allows the most selective deposition into the alveoli. A jet nebulizer (Respirgard II) with 2 ml volume fill (R2), and an ultrasonic nebulizer (Ultraneb 99) with 4 ml volume fill (U4), were compared using a 40-mg dose of MP labelled "Tcm human serum albumin. Particle size and MP-to-albumin binding were measured in the aerosol cloud. Each nebulizer was used in random order in five healthy volunteers. A dynamic posterior scan of 68 images of 15 s each was performed with a Gammatome II gamma camera during inhalation. Peripheral and central regions of interest were automatically defined with reproducible methods, and the peripheral-to-central ratio was used as a penetration index. Stomach and oropharynx activities were estimated on static anterior and static left lateral views, respectively, at the end of the examination. The mass median aerodynamic diameter (MMAD) was lower for R2 when unlabelled MP was used. The MMAD of MP+HSA was compatible with alveolar targeting. In the aerosol cloud, MP-albumin binding was 75% for R2 and 79% for U4. Peripheral and central activities at equilibrium (13-16 min) were higher with U4, but the penetration index was significantly higher with R2. Moreover, the stomach and oropharynx activities were significantly lower with R2. Granulometric study has shown that alveolar targeting of MP is possible, while granulometric and scintigraphic studies suggest that R2 produces more alveolar deposition of MP than U4.