Assessing dry powder inhalers

To enable what would otherwise be impractical, invasive and potentially dangerous testing, and to remove the huge variation and costs associated with human subjects, it is common practice to test inhalation devices and formulations using in vitro test apparatus. Industry standard test conditions and relevant parameters have been devised and published by the regulatory authorities and within the pharmacopoeias to enable accurate comparisons between data sets. For dry powder inhalers (DPIs) performance is a function of the applied breathing profile and this is reflected in the developed methodologies. However, while standardised protocols are an essential aspect of efficient research and routine equivalency testing, the recommended representative inhalation profile does not attempt to accurately reflect performance across the entire patient population.