Manipulation of Beclomethasone–Hydrofluoroalkane Interactions using Biocompatible Macromolecules

Investigations into the Formulation of Metered Dose Inhalers of Salmeterol Xinafoate and Fluticasone Propionate Microcrystals

“…Suspension stability is essentially a function of the physicochemical properties of the material interface with the propellant (26). Stability depends on van der Waals' dispersive forces and electrostatic interactions (27) between particles which can lead to strong short-range cohesive forces (13). Cohesive forces due to incompatibility with the dispersion medium leads to particulate aggregation.…”

Effect of moisture on the electrostatic charge properties of metered dose inhaler aerosols

“…The anion attracting ability of fluorine atoms was also alluded to by Yatsuzuka, Mizuno, & Asano (1994) in the discussion on the negative charging of Teflon after contact with water droplets. Furthermore, HFA-134a is more polar than 227ea (dipole moment 2.058 vs. 0.93 debye; dielectric constant 9.5 vs. 4.1) (Jones et al, 2006;Solvay Fluor, 2004). The more polar a molecule, the stronger are its electrostatic forces, thus it should become charged easier.…”

“…Five puffs of propellant aerosols with and without crystal violet were sized by spraying horizontally across the laser beam. The refractive indices of HFA-134a and 227ea were 1.17 and 1.22, respectively (Jones, Martin, & Brown, 2006). The imaginary refractive index used was 0.00 for both propellants.…”

Determination of Reference Ultrasound Parameters for Model and Hydrofluoroalkane Propellants Using High-Resolution Ultrasonic Spectroscopy

“…The majority of the techniques used to analyze characteristics such as particle size and stability are "indirect", e.g. light diffraction (1)(2)(3)(4)(5), light scattering (6,7), post-actuation studies (8)(9)(10) or the use of model propellant (11). Despite their lowtech nature, visual and manual sedimentation analytical methods are still widely employed (12)(13)(14).…”

“…Despite their lowtech nature, visual and manual sedimentation analytical methods are still widely employed (12)(13)(14). The most commonly utilized method, laser diffraction, is relatively inexpensive, fast, and reliable for measuring particle size distribution (PSD) of pressurized metered dose inhaler suspensions (10) in hydrofluoroalkane propellants (HFAs). However, the low boiling points and high vapor pressure of HFA propellants limits their analysis to a transparent sealed system after highpressure filling, making in situ analysis awkward with existing techniques.…”