Nasal drug delivery can be assessed by a variety of means and regulatory\nagencies, e.g., the Food and Drug Administration (FDA) and the European Medicines\nAgency (EMA) have published a set of guidelines and regulations proposing in vitro test\nmethods for the characterization of nasal drug products. This article gives a summary of\nthe FDA and EMA requirements regarding the determination of droplet size distribution\n(DSD), plume geometry, spray pattern and shot weights of solution nasal sprays and\ndiscusses the analytical challenges that can occur when performing these measurements.\nIn order to support findings from the literature, studies were performed using a standard\nnasal spray pump and aqueous model formulations. The aim was to identify possible\nmethod-, device- and formulation-dependent influencing factors. The literature review, as\nwell as the results from the studies show that DSD, plume geometry and spray pattern are\ninfluenced by, e.g., the viscosity of the solution, the design of the device and the actuation\nparameters, particularly the stroke length, actuation velocity and actuation force.\nThe dominant factor influencing shot weights, however, is the adjustment of the actuation\nparameters, especially stroke length and actuation velocity. Consequently, for routine\nmeasurements assuring, e.g., the quality of a solution nasal spray or, for in vitro\nbioequivalence studies, the critical parameters, have to be identified and considered in\nmethod development in order to obtain reproducible and reliable results.
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