COMPARISON OF JET AND ULTRASONIC NEBULIZERS FOR ALVEOLAR TARGETING OFMETHYLPREDNISOLONE

The secondary systemic effects of oral corticosteroid therapy in chron ic lung disease indicate the possible benefits of local therapy. The a im 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 je t nebulizer (Respirgard II) with 2 ml volume fill (R2), and an ultraso nic nebulizer (Ultraneb 99) with 4 ml volume fill (U4), were compared using a 40-mg dose of MP labelled Tc-99(m) human serum albumin. Partic le 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 re gions 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 a nd static left lateral views, respectively, at the end of the examinat ion. The mass median aerodynamic diameter (MMAD) was lower for R2 when unlabelled MP was used. The MMAD of MP+HSA was compatible with alveol ar targeting. In the aerosol cloud, MP-albumin binding was 75% for R2 and 79% for U4. Peripheral and central activities at equilibrium (13-1 6 min) were higher with U4, but the penetration index was significantl y higher with R2. Moreover, the stomach and oropharynx activities were significantly lower with R2. Granulometric study has shown that alveo lar targeting of MP is possible, while granulometric and scintigraphic studies suggest that R2 produces more alveolar deposition of MP than U4.