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Predicting HFA-MDI Dose Retention Properties: Engineering the Marriage between Canisters, Valves and Formulations

Lewis DA, O'Shea H, Johnson R, Church T.

RDD Europe 2011. Volume 1, 2011: 89-100.

Abstract:

The ability for the metering chamber of a metered dose inhaler (MDI) to retain a dose is dependent on the marriage between canister, valve and formulation. Combining high thermal conductivity, metal canisters with insulating polymeric valve components may generate transient localized thermal differentials, causing the content of the metering chamber to be under greater pressure than that within the canister, which may cause drainage of formulation from the metering chamber. The addition of ethanol to a formulation appears to reduce the liquid-vapor phase transitions, and prevents loss of prime caused by thermal gradients between the formulation reservoir and metering chamber. Prediction of an MDI’s dose retention performance may be possible if the materials of canister and valve construction, and details of the formulation are understood.