The second in a series of articles from the IPAC-RS Cascade Impaction Working Group concerning the limitations of metrics commonly used in the assessment of aerodynamic particle size distributions (APSDs) of orally inhaled products (OIPs). This article explores the limitations of stage groupings, probing whether they are suitable for making batch disposition decisions based on inhaler performance testing.
The authors suggest that impaction data is fundamentally flawed and ineffective because individual stage groupings do not adequately account for both dimensions of the size-fractionated mass comprising the APSD, and their combined use compounds this weakness to dramatic effect. Clearly, they say, stage groupings cannot be relied upon for batch-disposition decisions and are therefore a liability to the guarantee of safe and efficacious medicine for the patient.
Read part one – The liability of fine particle dose (FPD)
Read part three – Efficient data analysis (EDA): Size, mass and common sense