Dry powder inhalers are increasingly popular for delivering drugs to the lungs for the treatment of respiratory diseases, but are complex products with multivariate performance determinants. Heuristic product development guided by in vitro aerosol performance testing is a costly and time-consuming process. This study investigated the feasibility of using artificial neural networks (ANNs) to predict fine particle fraction (FPF) based on formulation device variables. Thirty-one ANN architectures were evaluated for their ability to predict experimentally determined FPF for a self-consistent dataset containing salmeterol xinafoate and salbutamol sulfate dry powder inhalers (237 experimental observations). Principal component analysis was used to identify inputs that significantly affected FPF. Orthogonal arrays (OAs) were used to design ANN architectures, optimized using the Taguchi method. The primary OA ANN r values ranged between 0.46 and 0.90 and the secondary OA increased the r values (0.53-0.93). The optimum ANN (9-4-1 architecture, average r 0.92 ± 0.02) included active pharmaceutical ingredient, formulation, and device inputs identified by principal component analysis, which reflected the recognized importance and interdependency of these factors for orally inhaled product performance. The Taguchi method was effective at identifying successful architecture with the potential for development as a useful generic inhaler ANN model, although this would require much larger datasets and more variable inputs.

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PurposeLow inspiratory force in patients with lung disease is associated with poor deagglomeration and high throat deposition when using dry powder inhalers (DPIs). The potential of two reverse flow cyclone prototypes as spacers for commercial carrier-based DPIs was investigated.MethodsCyclohaler®, Accuhaler® and Easyhaler® were tested with and without the spacers between 30 and 60 Lmin−1. Deposition of particles in the next generation impactor and within the devices was determined by high performance liquid chromatography.ResultsReduced induction port deposition of the emitted particles from the cyclones was observed due to the high retention of the drug within the spacers (e.g. salbutamol sulphate (SS): 67.89 ± 6.51% at 30 Lmin−1 in Cheng 1). Fine particle fractions of aerosol as emitted from the cyclones were substantially higher than the DPIs alone. Moreover, the aerodynamic diameters of particles emitted from the cyclones were halved compared to the DPIs alone (e.g. SS from the Cyclohaler® at 4 kPa: 1.08 ± 0.05 μm vs. 3.00 ± 0.12 μm, with and without Cheng 2, respectively) and unaltered with increased flow rates.ConclusionThis work has shown the potential of employing a cyclone spacer for commercial carrier-based DPIs to improve inhaled drug delivery.

This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.Deagglomeration of cohesive particles in combination with coarse carrier is a key requirement for inhaled formulations. The aim of the project was to propose a mathematical approach to understand aerosolization behaviour of micronized particles alone and in formulation with carriers. Salbutamol sulphate and salmeterol xinafoate were blended separately with fine lactose (ratio 1:4) and fine and coarse lactose (1:4:63.5). Laser diffraction was employed to characterize the powder median particle size. The deagglomeration of micronized materials followed an asymptotic monoexponential relationship. When the coarse lactose was added, the relationship fitted a bi-exponential equation showing an easily and a poorly dispersed fraction. Using model hydrophobic and hydrophilic APIs, this study has demonstrated the utility of an analytical approach that can parameterize deagglomeration behaviour of carrier-free and carrier-based inhalation formulations. The analytical approach provides the ability to systematically study the effect of material, formulation and processing factors on deagglomeration behaviour