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In vitro-in vivo correlation is the establishment of a predictive relationship between in vitro and in vivo data. In the context of cascade impactor results of orally inhaled pharmaceutical aerosols, this involves the linking of parameters such as the emitted dose, fine particle dose, fine particle fraction, and mass median aerodynamic diameter to in vivo lung deposition from scintigraphy data. If the dissolution and absorption processes after deposition are adequately understood, the correlation may be extended to the pharmacokinetics and pharmacodynamics of the delivered drugs. Correlation of impactor data to lung deposition is a relatively new research area that has been gaining recent interest. Although few in number, experiments and meta-analyses have been conducted to examine such correlations. An artificial neural network approach has also been employed to analyse the complex relationships between multiple factors and responses. However, much research is needed to generate more data to obtain robust correlations. These predictive models will be useful in improving the efficiency in product development by reducing the need of expensive and lengthy clinical trials., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

A volume-based Monte Carlo simulation describing the distribution of polydisperse particles aerosolized in polydisperse droplets was developed. The algorithm addressed some major limitations found in previous models, particularly when the assumptions of the Poisson distribution, a parametric distribution frequently employed to describe the distribution process both deterministically and stochastically, may be less justified. A total of 144 simulations were conducted over combinations of four formulation factors, namely, the suspension concentration c, the ratio of the mass median diameter of the droplets to that of the particles R, and the geometric standard deviation of the droplet σ d and that of the particle σ p . Using the current algorithm, we found good agreements between simulated results and those from previous studies. The composition uniformity of the resultant clusters was improved with increasing c and/or R, and decreasing σ p and σ d . The exhaustive distribution of all simulated particles also allowed ready adaptation to infer other statistics of interest, such as the aerodynamic diameter of the resultant clusters. This approach is useful for prediction of the particle size distribution and chemical composition of powders produced by aerosolization and spray drying of suspensions., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Aerosols emitted from metered dose inhalers (MDIs) are generally electrically charged and bipolar in nature. Although a spacer can effectively dampen the charge magnitude of aerosols, the electrostatic interactions between the positively and negatively charged particles and the spacer have not yet been characterized separately. The Bipolar Charge Analyzer (BOLAR) was employed to investigate interactions between the spacer and the charged aerosols. Three individual actuations of Tilade ® MDI were introduced without a spacer and through an antistatic AeroChamber Plus ® Z Stat ® , an uncoated and a detergent-coated AeroChamber Plus ® spacer into the BOLAR at 60 L/min. Charge and mass profiles were determined. The surface potential of spacers followed the order of uncoated > detergent-coated > antistatic spacer. The spacers had minimal impact on the positively charged particles but the charge magnitude of the negatively charged particles was in the opposite order as the spacer surface potential. The charge-to-mass ratio of particles had little alteration for all measurements. Negatively charged particles had a higher tendency to deposit on the spacer walls, possibly due to their higher abundance in the confined spacer volume. The bipolar data may prove useful for designing better MDIs and spacers and modelling lung deposition of charged aerosol particles., (Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.)