Spray Pattern and Plume Geometry Testing and Methodology: An IPAC-RS Working Group Overview.

Plume characterization for orally inhaled and nasal drug products (OINDP) provides valuable information during OINDP development. Spray pattern and plume geometry techniques, methods, and technology have evolved over the past 20 years since the publication of the original 1998 FDA MDI DPI draft guidance. The International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS) discusses the historical context and background to plume geometry and spray pattern characterization studies; provides an analysis of the current regulatory context; addresses results from its industry surveys on application and value of such testing; and presents case studies and best practices-seeking to provide insights to regulatory bodies and other stakeholders. Assessment and consideration of published studies and industry experience note the value of plume geometry and spray pattern in development, and that further data is needed regarding their use in assessing formulation characteristics. Continued dialogue between industry and regulatory bodies is needed to establish the optimum use of these techniques.

A modified USP induction port to characterize nasal spray plume geometry and predict turbinate deposition under flow.

There is currently no in vitro technique for assessing plume geometry of nasal sprays under airflow conditions. However, a majority of FDA approved nasal products recommend that patients inhale during actuation. Therefore, a reproducible in vitro test that measures plume angles under physiologically relevant inhalation flow rates would be useful. The purpose of this study was to adapt the recently described Plume Induction Port Evaluator (PIPE) apparatus for nasal sprays under flow and correlate these with nasal cast deposition patterns. Mass Median Plume Angles (MMPAs) of four nasal spray formulations with increasing viscosities were determined using the PIPE apparatus in the absence and presence of airflow. MMPAs were then correlated to drug deposition within 3D printed nasal casts using airflow. We evaluated different inhalation instructions obtained from the package insert of nasal products. MMPAs significantly reduced (narrower angles) when using flow for the three formulations with the lowest viscosities. An increase in the turbinate deposition was observed in the nasal casts when just one of the nostrils was closed during inhalation, except by the highest viscosity formulation. The turbinate deposition numerically correlated with changes in the plume angles observed using PIPE.

Effect of Inhalation Flow Rate on Mass-Based Plume Geometry of Commercially Available Suspension pMDIs.

Although high-speed laser imaging is the current standard to characterize the plume angle of suspension-based pressurized metered dose inhalers (pMDIs), this method is limited by the inability to identify the drug content in a droplet and simulate inhalation flow. The Plume Induction Port Evaluator (PIPE) is a modified induction port for cascade impactors that allows for the calculation of the angle of a plume based on direct drug mass quantification rather than indirect droplet illumination under airflow conditions. The objective of this study was to investigate the use of the PIPE apparatus to evaluate the effect of airflow on the Mass Median Plume Angle (MMPA) of commercially available suspension-based pMDIs (Ventolin® HFA, ProAir® HFA, and Proventil® HFA). Deposition patterns within PIPE were log-normally distributed allowing for the calculation of the MMPA for the three suspension products. Mass-based plume angles were significantly smaller (narrower angle) when inhalation airflow was used compared to no flow conditions (reduction of MMPA was 8, 16, and 13% for Ventolin® HFA, ProAir® HFA, and Proventil® HFA, respectively). Additionally, new parameters for characterizing plume geometry were calculated (MMPA ex-actuator and plume orientation). Mass-based plume angles of the suspension-based pMDI formulations were highly reproducible and demonstrated the effect of inhalation flow rate. These results suggest that plume geometry tests should be evaluated under flow conditions which is not possible using current methodologies. Graphical Abstract ᅟ.

High-Speed Laser Image Analysis of Plume Angles for Pressurised Metered Dose Inhalers: The Effect of Nozzle Geometry.

The aim of this study is to investigate aerosol plume geometries of pressurised metered dose inhalers (pMDIs) using a high-speed laser image system with different actuator nozzle materials and designs. Actuators made from aluminium, PET and PTFE were manufactured with four different nozzle designs: cone, flat, curved cone and curved flat. Plume angles and spans generated using the designed actuator nozzles with four solution-based pMDI formulations were imaged using Oxford Lasers EnVision system and analysed using EnVision Patternate software. Reduced plume angles for all actuator materials and nozzle designs were observed with pMDI formulations containing drug with high co-solvent concentration (ethanol) due to the reduced vapour pressure. Significantly higher plume angles were observed with the PTFE flat nozzle across all formulations, which could be a result of the nozzle geometry and material's hydrophobicity. The plume geometry of pMDI aerosols can be influenced by the vapour pressure of the formulation, nozzle geometries and actuator material physiochemical properties.