Health & Environmental Research Online (HERO)


Print Feedback Export to File
2542393 
Journal Article 
A correlation equation for the mass median aerodynamic diameter of the aerosol emitted by solution metered dose inhalers 
Ivey, JW; Lewis, D; Church, T; Finlay, WH; Vehring, R 
2014 
Yes 
International Journal of Pharmaceutics
ISSN: 0378-5173
EISSN: 1873-3476 
465 
1-2 
18-24 
English 
24524827 
WOS:000333675100004 
A correlation equation for the mass median aerodynamic diameter (MMAD) of the aerosol emitted by solution metered dose inhalers (MDIs) is presented. A content equivalent diameter is defined and used to describe aerosols generated by evaporating metered dose inhaler sprays. A large set of cascade impaction data is analyzed, and the MMAD and geometric standard deviation is calculated for each datum. Using dimensional analysis, the mass median content equivalent diameter is correlated with formulation variables. Based on this correlation in combination with mass balance considerations and the definition of the aerodynamic diameter, an equation for prediction of the MMAD of an inhaler given the pressure of the propellant in the metering chamber of the MDI valve and the surface tension of the propellant is derived. The accuracy of the correlation equation is verified by comparison with literature results. The equation is applicable to both HFA (hydrofluoroalkane) propellants 134a and 227ea, with varying levels of co-solvent ethanol. 
Solution metered dose inhaler; Mass median aerodynamic diameter; Dimensional analysis; Droplet diameter distribution; Content equivalent diameter 
NAAQS
• ISA-PM (2019)