title: Physicochemical factors governing the performance of nedocromil sodium as a dry powder aerosol.
abstract: Previous investigations have found that the in vitro aerosol performance of nedocromil sodium is poor. A study has been undertaken to gain a better understanding of the physicochemical properties of the drug particles together with the factors governing the aerosol performance of inhalation systems containing this drug. Material previously passed through a hammer mill only and particles subsequently passed through a micronizer were characterized, and the information gathered was correlated with the in vitro aerosol performance of the pure drug systems. Optimization of particle sizing procedures revealed that both sets of materials were ultrafine powders with a volume median diameter of approximately 1 microm. It is concluded that the processing stages, employed in the manufacture of these batches of fine particle nedocromil sodium trihydrate, may not in fact be primary particle size reduction stages but instead deaggregation stages and that these govern the aerosol performance. The in vitro aerosol performance of samples of the "micronized" nedocromil sodium stored over a range of relative humidities (RHs) was characterized. Storage RHs in the range 12-76% (where nedocromil sodium is stable as the trihydrate) did not have a dramatic effect on the in vitro aerosol performance of the drug. However, conversion to the heptahemihydrate (following storage of the drug at 86% RH) significantly decreased the deaggregation performance in an in vitro model.
authors.affiliation: Aerosol Research Group, Department of Pharmaceutics, Virginia Commonwealth University, Richmond, Virginia 23298, USA. mjclarke@hsc.vcu.edu
authors.forename: M J
authors.initials: MJ
authors.lastname: Clarke
authors.forename: M J
authors.initials: MJ
authors.lastname: Tobyn
authors.forename: J N
authors.initials: JN
authors.lastname: Staniforth
mesh_terms: D000280:Administration, Inhalation; D000336:Aerosols; D018927:Anti-Asthmatic Agents / Q000008:administration & dosage / Q000737:chemistry*; D003080:Cold Temperature; D003460:Crystallization; D003890:Desiccation; D004356:Drug Storage; D006813:Humidity; D008855:Microscopy, Electron, Scanning; D017835:Nedocromil / Q000008:administration & dosage / Q000737:chemistry*; D010316:Particle Size; D011208:Powders; D013678:Technology, Pharmaceutical / Q000379:methods; D014867:Water / Q000032:analysis / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D000336:Aerosols; D018927:Anti-Asthmatic Agents; D011208:Powders; D014867:Water; D017835:Nedocromil