title: A correlation equation for the mass median aerodynamic diameter of the aerosol emitted by solution metered dose inhalers.
abstract: 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.
authors: Department of Mechanical Engineering, University of Alberta, Edmonton, Canada.
authors: James W
authors: JW
authors: Ivey
authors: Chiesi Ltd., Chippenham, United Kingdom.
authors: David
authors: D
authors: Lewis
authors: Chiesi Ltd., Chippenham, United Kingdom.
authors: Tanya
authors: T
authors: Church
authors: Department of Mechanical Engineering, University of Alberta, Edmonton, Canada.
authors: Warren H
authors: WH
authors: Finlay
authors: Department of Mechanical Engineering, University of Alberta, Edmonton, Canada. Electronic address: reinhard.vehring@ualberta.ca.
authors: Reinhard
authors: R
authors: Vehring
mesh_terms: D000280:Administration, Inhalation; D000335:Aerosol Propellants; D000336:Aerosols; D002626:Chemistry, Pharmaceutical; D016503:Drug Delivery Systems / Q000295:instrumentation*; D000431:Ethanol / Q000737:chemistry; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry; D036501:Metered Dose Inhalers; D008956:Models, Chemical; D010316:Particle Size; D004364:Pharmaceutical Preparations / Q000008:administration & dosage* / Q000737:chemistry*; D011312:Pressure; D012997:Solvents / Q000737:chemistry; D013500:Surface Tension; D005466:Fluorocarbons
chemical_list: D000335:Aerosol Propellants; D000336:Aerosols; D000431:Ethanol; D006845:Hydrocarbons, Fluorinated; D004364:Pharmaceutical Preparations; D012997:Solvents; C094049:apaflurane; D005466:Fluorocarbons
keywords: Content equivalent diameter; Dimensional analysis; Droplet diameter distribution; Mass median aerodynamic diameter; Solution metered dose inhaler