Probing the Aerodynamic Particle Size Distribution of Dry Powder Inhaler Combination Products Foster® NEXThaler® and Seretide® Diskus® using Single Particle Aerosol Mass Spectrometry (SPAMS)
Bradley Morrical1, Martin Jetzer & Stephen Edge
Novartis Pharma AG, Global Development, Novartis Campus, Lichtstrasse 35, Basel, 4056, Switzerland
The invitro aerosol performance of two combination dry powder inhaler (DPI) products, Foster® NEXThaler® and Seretide® Diskus® were investigated with single particle aerosol mass spectrometry (SPAMS). The in-vitro pharmaceutical performance is markedly different for both inhalers. Foster® NEXThaler® generates a higher fine particle fraction (FPF <5 μm) and a much higher relative extra fine particle fraction (eFPF <2 μm). In terms of the composition of the aerodynamic particle size distribution (APSD), it could be verified with SPAMS that overall Foster® NEXThaler® emits a significantly higher number of fine and extra fine particles. Additionally, the interactions between the two active pharmaceutical ingredients (APIs) in both products are different. While Seretide® Diskus® emits a significant (37%) number of co-associated API particles, only a negligible number of co-associated API particles were found in Foster® NEXThaler® (<1%). A major difference with Foster® NEXThaler® is that it contains magnesium stearate (MgSt) as a second excipient besides lactose in a so-called ‘dual excipient’ platform. The data generated using SPAMS suggested that nearly all of the beclomethasone dipropionate particles in Foster® NEXThaler® also contain MgSt and must therefore be co-associated with this additional excipient. This may help explain why beclomethasone dipropionate in Foster® NEXThaler® forms less particle co-associations with the second API, formoterol fumarate, shows a lower cohesive strength in respect to beclomethasone itself and why both APIs exhibit superior detachment from the carrier as evidenced by the increased eFPF and smaller median aerodynamic diameter (MAD).