The pulmonary deposition of two aerosol preparations of nedocromil sodium delivered by MDI assessed by single photon emission computed tomography.

ABSTRACT The pulmonary deposition and pharmacokinetics of fine and coarse radioactive aerosols of nedocromil sodium, of mass median aerodynamic diameters 16μm and 24μm respectively, delivered by metered dose inhaler (MDI) have been investigated. The corresponding geometric standard deviations of the particle size distributions were 5.32 and 3.93. Pulmonary deposition was assessed by both planar radionuclide scintigraphy and multi-modality three dimensional imaging using single photon emission computed tomography (SPECT) and x-ray computed tomography (CT). The three dimensional data were analysed by transformation to a hemispherical shape based on the fractional radial distance of each point in the lung from the centre to the corresponding extrapolated point on the periphery. This enabled parameters on the variation of both concentration of deposition and total amount deposited with penetration distance to be calculated. For both planar and SPECT data the central to peripheral concentration ratio (C/P rati...