Exploring the impact of formulation and temperature shock on metered dose inhaler priming

Abstract

ABSTRACTThe interplay between canister, valve design, formulation, and environmental temperature is crucial to dose retention in metered dose inhalers (MDIs). Previous studies that have utilized MDIs with polymeric capillary retention valves, have shown that exposure to environmental changes can create a temporary temperature gradient between the formulation retained in the metering chamber and the formulation reservoir in the metal canister, which can cause inconsistencies in the dose delivered to the patient. The purpose of this study was to more fully quantify these effects. This was achieved by deliberately varying the temperature difference between inhalers and environment within ranges representative of routine usage, and assessing the resulting loss of prime effect via shot weight and delivered dose testing.The shot weights delivered by three fixed-dose commercial MDIs—Foster®, flutiform® and Seretide®, were investigated under different experimental conditions. Exposure to temperature changes of up...