METERED-DOSE INHALERS .2. PARTICLE-SIZE MEASUREMENT VARIATION

Three apparatuses, the Andersen Cascade Impactor (ACI), the Marple-Mil ler Impactor (MMI) and the Twin Impinger (TI) were compared in the mea surement of particle size distribution (PSD) of four commercially avai lable salbutamol metered-dose inhalers (MDIs). The ACI was fitted with two induction ports. One was that currently described in the United S tates Pharmacopeia (USP) and the second had a larger volume. Parameter s calculated included Mass Median Aerodynamic Diameter (MMAD), Geometr ic Standard Deviation (GSD) and Fine Particle Dose (FPD). The results demonstrated that several of these parameters were device-dependent an d that all of the apparatuses were able to detect differences between some of the MDIs. The larger induction port allowed more drug substanc e to enter the ACI which may be advantageous in some PSD work. (C) 199 7 Elsevier Science B.V.