Investigation of nozzle designs and material on the electrostatic charge of pressurised metered dose inhaler

Yang Chen, Daniela Traini, David F. Fletcher, Hak Kim Chan, David Lewis, Tanya Church, Paul M. Young

Background: Electrostatic charge plays an important role in particle deposition in pressurised metered dose inhaler (pMDI) and is influenced by factors, such as chemical/physical properties of the formulation and device materials. Charges can accumulate at the sharp edges of the pMDI actuator, leading to electrostatic discharge to the surrounding environment and causing changes in inhalation aerosol charge profile. In this study the influence of different nozzle designs, using conducting and insulating actuator materials, on pMDI aerosols performance was investigated.
Methods: Two actuator materials (aluminium and polyethylene terephthalate), each with four types of nozzle designs (flat, curved flat, cone and curved cone) were tested using the electrical low-pressure impactor (ELPI) for the determination of their electrostatic charge profiles. Beclomethasone (BDP) pMDI solution was chosen as model formulation and drug deposition was analyzed and assayed using high performance liquid chromatography (HPLC).
Results: Curved nozzle designs for the insulating PET actuator significantly influenced charge profiles (-ve polarity to +ve polarity) and drug deposition (ANOVA, p<0.05) compared with the metal aluminium actuator. These results are probably due to the change of plume geometry imparted by the curved edge nozzle design. Aluminium flat nozzle shown significantly higher electronegative charge (-249.45pC ± 77.22) and higher induction port deposition (66.78 % of total exvalve dose), indicating particle deposition is influenced by the electrostatic charge magnitude.
Conclusion: The property of the actuator materials and nozzle designs could both influence aerosol electrostatic charges suggesting that, by choosing different nozzle design and actuator materials combination, drug deposition pattern for pMDI formulations could be altered.

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