Abstract
Background
The recent development of non-chlorofluorocarbon propellant formulations for pressurized metered-dose inhalers prompts the need for the comparative evaluation of dose delivery by small- versus large-volume holding chambers (HCs). The performance of 2 representative large- and small-volume HCs has been investigated with chlorofluorocarbon-formulated albuterol (Ventolin) and hydrofluoroalkane-formulated albuterol sulfate (Airomir) with the objective of studying the influence of chamber capacity on so-called "fine-particle" dose and total dose. Three Aero-Chamber and a similar number of Volumatic HCs were tested with each formulation.
Methods
An 8-stage Andersen cascade impactor was used to determine mass-weighted size distributions of drug delivered at the mouthpiece of each HC. The mass of albuterol (Ventolin) or albuterol sulfate (Airomir) collected in the impactor was assayed by high performance liquid chromatography with ultraviolet detection in order to measure both fine-particle dose (< 4.7-µm aerodynamic diameter) and total dose.
Results
For Ventolin, the fine-particle and total doses were 45.4 ± 0.3 µg and 47.2 ± 0.1 µg, respectively, for the AeroChamber HC and 63.8 ± 2.3 µg and 66.1 ± 3.0 µg, respectively, for the Volumatic HC. For Airomir, the fine-particle and total doses expressed as albuterol base equivalent were 62.0 ± 2.9 µg and 64.2 ± 3.0 µg, respectively, for the AeroChamber HC and 67.9 ± 2.5 µg and 69.7 ± 3.4 µg, respectively, for the Volumatic HC.
Conclusions
There was a significant difference in both fine-particle and total dose between large- and small-volume HCs with Ventolin (unpaired t test, p < 0.001). However, both HCs performed similarly with Airomir (p = 0.056). In all cases, the available dose from the HCs comprised > 95% of fine particles.
Keywords
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