I had a great time at this year’s Respiratory Drug Delivery Europe conference! Berlin was as stunning as ever.
As well as nosing around the rest of the conference and exhibition, Dr Julie Suman, President of NextBreath LLC and I co-hosted an interactive workshop where we considered whether the methods that are applied to the characterization of liquid nasal sprays, as described in the FDA’s Bioequvalence and Bioavailability draft guidance for locally acting nasal aerosols and sprays, are relevant to dry powder devices. Within this, we discussed how aerosol particle size characterisation and spray plume measurements may provide a way of understanding how effective powder dispersion and delivery can be achieved.
Testing nasal dry powder delivery devices
Over the past few years, there has been increased interest in the use of nasal dry powder delivery systems, due to the advantages powder formulations offer in terms of stability and patient compliance. This has seen dry powder devices being considered for the delivery of a range of compounds, including vaccine delivery. However, guidance on how these devices should be characterized is currently not in place. At our workshop we presented recent research to demonstrate that laser diffraction particle sizing is appropriate for characterizing nasal dry powder devices. Additionally, the development of the Morphologi G3-ID now also allows chemical identification of particles, providing extra insight during formulation development.
Nasal dry powder devices present many challenges, delivering a high concentration of powder in a very short time scale compared to liquid devices. Using the Spraytec laser diffraction system, it is possible to acquire data at 100 microsecond intervals, allowing the changes in particle size and concentration to be monitored precisely during device acquisition. This allowed us to understand how changes to the device actuation profile affected the dispersion of the dry powder. Then, using the Proveris Scientific SprayVIEW imaging system, we were able to correlate these results with the observed changes in plume angle. From this, we were able to show that, although the applied actuation velocity does affect dispersion, there is little change in the plume shape.
Of course, one issue with using light scattering techniques is that the identity of the particles being measured cannot be confirmed. This is particularly an issue with dry powder formations, where the drug may be present with one of more excipients. So, we ended the workshop by describing techniques which do allow the particle size of the drug to be characterised. This included new methods for impactor measurements, using nasal casts, as well as the application of the Morphologi G3-ID Raman chemical imaging system, which allows the particle size and composition of powder formulations to be studied.
Workshop a success!
I have to say that I enjoyed presenting alongside Dr Suman and wish to take this opportunity to thank her once again! I’d also like to thank all those who attended. If you did, and we did not get a chance to talk at the time, do get in touch!