Nasal application of spray-dried powders – the impact of filling processes on deposition in a nasal cast

Nasal powders can be advantageous to liquid formulations due to increased stability. A concern of nasal powders could be a changed deposition behaviour after being subjected to compaction during the filling process. Therefore, in this study, spray-dried formulations with the size of 20 - 30 µm differing in morphology (spherical and wrinkled) and surface polarity (hydrophilic and hydrophobic) were assessed in a nasal cast regarding their deposition profile in an uncompacted and compacted state (state owing to the filling processes). The aim was to investigate whether dosing processes with different dosing systems (dosator and vacuum drum), which physically stress the powder and may result in increased cohesion, influence dispersion and deposition. For this purpose, the formulations were dosed into a unit dose system for powders (UDS powder) with both systems at different fill weights and compared to manually filled powders with respect to the deposition profile. The results showed that the dosing process can lead to an increased deposition of hydrophilic powders in the turbinate area at breath hold compared to unprocessed material, which is favourable, because this is a target area for systemic drug uptake. Application during normal breathing (15 L/min) showed no positive influence of the dosing process but a shift in deposition to postnasal areas, which is unfavourable in intranasal drug delivery.