Pulmonary dispersion formulations: The impact of dispersed powder properties on pressurized metered dose inhaler stability

Abstract

Suspension-type metered dose inhaler formulations characteristically have a high degree of dispersion instability. This may occur as the result of any of a large number of formulation issues including phase separation, particle growth, agglomeration/flocculation, moisture ingress, and particle interactions with both the canister material and other particles. Many of these undesirable instabilities may arise as a result of the physical and chemical properties of the dispersed powder in the liquid propellant system. As such, this review provides a detailed understanding of the characteristics of the dispersed phase in the liquid propellant system necessary to ensure stability of the final formulation.

Keywords::

• Pressurized
• inhaler
• propellant
• stability
• canister
• particle size
• density
• atomic force microscopy
• van der Waals