In Parts I and II of this series, we introduced the concept that the batch release criteria for OIPs can and should dictate the quality constraints on all cascade impactors (CIs) used for batch release testing. This logical proposition applies to the entire set of analytical equipment involved in the making and testing of a commercial drug product. However, the current approach to CI quality specifications requires only a verification of the diameter of nozzles of each stage along with a requirement that the flow rate during testing be known within ± 5% of a target value. Here, we ask two questions: Are these requirements necessary? And are these requirements sufficient? Our thesis is that the inhaler testing community, both from the manufacturer and regulator perspectives, should insist that the CI quality specifications be both necessary and sufficient for the testing of batches of drug product for release of that product to the public.
See Part I: A grassroots look
See Part II: The concept of “sufficient” as applied to impactor quality specifications