title: Comparison of in vitro and in vivo efficiencies of a novel unit-dose liquid aerosol generator and a pressurized metered dose inhaler.
abstract: Gamma scintigraphic imaging was employed in 10 healthy volunteers to compare the total and regional lung deposition of aerosols generated by two delivery platforms that permitted microprocessor-controlled actuation at an optimal point during inhalation. An aqueous solution containing 99mTc-DTPA was used to assess the deposition of aerosols delivered by inhalation from two successive unit-dosage forms (44 microl volume) using a prototype of a novel liquid aerosol system (AERx Pulmonary Delivery System). This was compared with aerosol deposition after inhalation of two 50 microl puffs of a 99mTc-HMPAO-labeled solution formulation from a pressurized metered dose inhaler (MDI). The in vitro size characteristics of the radiolabeled aerosols were determined by cascade impaction. For the AERx system, the predicted lung delivery efficiency based on the product of emitted dose (60.8%, coefficient of variation (CV)=12%) and fine particle fraction (% by mass of aerosol particles <5.7 microm in diameter) was 53.3% (CV=13%). For the solution MDI, the emitted dose was 62.9% (CV=13%) and the predicted lung dose was 44. 9% (CV=15%). The AERx system demonstrated efficient and reproducible dosing characteristics in vivo. Of the dose loaded into the device, the mean percent reaching the lungs was 53.3% (CV=10%), with only 6. 9% located in the oropharynx/stomach. In contrast, the lung deposition from the solution MDI was significantly less (21.7%) and more variable (CV=31%), with 42.0% of the radiolabel detected in the oropharynx/stomach. Analysis of the regional deposition of the radioaerosol indicated a homogeneous pattern of deposition after delivery from the AERx system. A predominantly central pattern of distribution occurred after MDI delivery, where the pattern of deposition was biased towards a central zone depicting the conducting airways. The AERx system, in contrast to MDIs, seems highly suited to the delivery of systemically active agents via pulmonary administration.
authors.affiliation: Aradigm Corporation, Hayward, CA 94545, USA. farrs@aradigm.com
authors.forename: S J
authors.initials: SJ
authors.lastname: Farr
authors.forename: S J
authors.initials: SJ
authors.lastname: Warren
authors.forename: P
authors.initials: P
authors.lastname: Lloyd
authors.forename: J K
authors.initials: JK
authors.lastname: Okikawa
authors.forename: J A
authors.initials: JA
authors.lastname: Schuster
authors.forename: A M
authors.initials: AM
authors.lastname: Rowe
authors.forename: R M
authors.initials: RM
authors.lastname: Rubsamen
authors.forename: G
authors.initials: G
authors.lastname: Taylor
mesh_terms: D000328:Adult; D000336:Aerosols; D006801:Humans; D007727:Krypton Radioisotopes; D008168:Lung / Q000000981:diagnostic imaging; D008297:Male; D009330:Nebulizers and Vaporizers; D011312:Pressure; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime; D016284:Technetium Tc 99m Pentetate
chemical_list: D000336:Aerosols; D007727:Krypton Radioisotopes; D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime; D016284:Technetium Tc 99m Pentetate