Effects of Formulation Variables on Lung Dosimetry of Albuterol Sulfate Suspension and Beclomethasone Dipropionate Solution Metered Dose Inhalers

Nicotine flux and pharmacokinetics-based considerations for early assessment of nicotine delivery systems

In the past few years, technological advancements enabled the development of novel electronic nicotine delivery systems (ENDS). Several empirical measures such as "nicotine flux" are being proposed to evaluate the abuse liability potential of these products. We explored the applicability of nicotine flux for clinical nicotine pharmacokinetics (PK) and 52-week quit success from cigarettes for a wide range of existing nicotine delivery systems. We found that the differences in nicotine flux for various nicotine delivery systems are not related to changes in PK, as nicotine flux does not capture key physiological properties such as nicotine absorption rate. Further, the 52-week quit success and abuse liability potential of nicotine nasal sprays (high nicotine flux product), and nicotine inhalers (nicotine flux similar to ENDS) are low, suggesting that nicotine flux is a poor metric for the assessment of nicotine delivery systems. PK indices are more dependable for characterizing nicotine delivery systems, and a nicotine plasmaC max T max > 1 could improve 52-week quit success from cigarettes. However, a single metric may be inadequate to fully assess the abuse liability potential of nicotine delivery systems and needs to be further studied. A combination of in vitro and in silico approaches could potentially address the factors influencing the inhaled aerosol dosimetry and resulting PK of nicotine to provide early insights for ENDS assessments. Further research is required to understand nicotine dosimetry and PK for ad libitum product use, and abuse liability indicators of nicotine delivery systems. This commentary is intended to (1) highlight the need to think beyond a single empirical metric such as nicotine flux, (2) suggest potential PK-based metrics, (3) suggest the use of in vitro and in silico tools to obtain early insights into inhaled aerosol dosimetry for ENDS, and (4) emphasize the importance of considering comprehensive clinical pharmacology outcomes to evaluate nicotine delivery systems.

Development of an Ethanol-Free Salbutamol Sulfate Metered-Dose Inhaler: Application of Molecular Dynamic Simulation-based Prediction of Intermolecular Interaction

INTRODUCTION

More than fifty years after the commercialization of the Ventolin metered-dose inhaler (MDI), its constituent active ingredient, salbutamol sulfate (SS) remains the most prescribed short-acting beta agonist for the first-line treatment of acute asthma attacks and the metered-dose inhaler remains its primary dosage form. The first generation of Ventolin MDI was developed at a time when environmental and regulatory concerns were less stringent than today. The MDI industry is now on the verge of a second major reformulation effort in response to environmental concerns. This paper serves to illustrate how modern computational modeling of molecular interactions can aid the reformulation process. By way of a case study, computational modeling was performed to compare poly(ethylene glycol) 400 (PEG400) and, separately, isopropyl myristate (IPM) as substitutes for the ethanol used in some generic salbutamol sulfate suspension-based hydrofluoroalkane MDIs.

METHODS

PEG400 and isopropyl myristate (IPM) were investigated as potential alternative cosolvents to ethanol in HFA134a-based SS suspension MDI formulations. Density functional theory (DFT) molecular dynamics simulations were used to evaluate the compatibility of the candidate cosolvents with the formulation's components. Corresponding physical formulations were filled into polyethylene terephthalate (PET) and, separately, aluminium canisters. In-vitro pharmaceutical product performance and macroscopic visual appearance were assessed and compared to the results of the simulation studies.

RESULTS

The simulation studies indicated that PEG400 would be a good candidate as a replacement for ethanol whereas IPM would not. The in-vitro and visual assessments support the predicted outcome of the simulation studies.

CONCLUSION

This work suggests that molecular dynamics simulations may provide a useful tool to aid the selection of compatible excipients when reformulating MDI suspension-based products, thereby reducing the time and cost associated with manufacturing and testing of physical samples.

Effect of MDI Actuation Timing on Inhalation Dosimetry in a Human Respiratory Tract Model

Accurate knowledge of the delivery of locally acting drug products, such as metered-dose inhaler (MDI) formulations, to large and small airways is essential to develop reliable in vitro/in vivo correlations (IVIVCs). However, challenges exist in modeling MDI delivery, due to the highly transient multiscale spray formation, the large variability in actuation–inhalation coordination, and the complex lung networks. The objective of this study was to develop/validate a computational MDI-releasing-delivery model and to evaluate the device actuation effects on the dose distribution with the newly developed model. An integrated MDI–mouth–lung (G9) geometry was developed. An albuterol MDI with the chlorofluorocarbon propellant was simulated with polydisperse aerosol size distribution measured by laser light scatter and aerosol discharge velocity derived from measurements taken while using a phase Doppler anemometry. The highly transient, multiscale airflow and droplet dynamics were simulated by using large eddy simulation (LES) and Lagrangian tracking with sufficiently fine computation mesh. A high-speed camera imaging of the MDI plume formation was conducted and compared with LES predictions. The aerosol discharge velocity at the MDI orifice was reversely determined to be 40 m/s based on the phase Doppler anemometry (PDA) measurements at two different locations from the mouthpiece. The LES-predicted instantaneous vortex structures and corresponding spray clouds resembled each other. There are three phases of the MDI plume evolution (discharging, dispersion, and dispensing), each with distinct features regardless of the actuation time. Good agreement was achieved between the predicted and measured doses in both the device, mouth–throat, and lung. Concerning the device–patient coordination, delayed MDI actuation increased drug deposition in the mouth and reduced drug delivery to the lung. Firing MDI before inhalation was found to increase drug loss in the device; however, it also reduced mouth–throat loss and increased lung doses in both the central and peripheral regions.

Systematic Evaluation of the Effect of Formulation Variables on In Vitro Performance of Mometasone Furoate Suspension-Metered Dose Inhalers

The therapeutic benefits of metered dose inhalers (MDIs) in pulmonary disorders are mainly driven by aerosol performance, which depends on formulation variables (drug and excipients), device design, and patient interactions. The present study provides a comprehensive investigation to better understand the effect of formulation variables on mometasone furoate (MF) suspension-based MDI product performance. The effects of MF particle size (volume median diameter; X50) and excipient concentration (ethanol and oleic acid, cosolvent, and surfactant, respectively) on selected critical quality attributes (delivered dose (DD), fine particle dose of particles lesser than 5 µm (FPD < 5), ex-throat dose and median dissolution time (MDT)) were studied. Eight MF-MDI formulations (one per batch) were manufactured based on a reduced factorial design of experiment (DOE) approach, which included relevant formulation levels with varying X50 (1.1 and 2 μm), concentration of ethanol (0.45, 0.9, 1.8, and 3.6%w/w), and oleic acid (0.001 and 0.025%w/w). The in vitro evaluation of these MF-MDI formulations indicated the importance of drug particle's X50, oleic acid, and ethanol canister concentration as critical formulation variables governing the performance of MF suspension-based MDI products. The effect of these formulation variables on DD, FPD < 5, ex-throat dose, and MDT was subsequently utilized to develop empirical relationships linking formulation factors with effects on in vitro performance measures. The developed strategy could be useful for predicting MF-MDI product performance during MDI product development and manufacturing. The systematic DOE approach utilized in this study may provide insights into the understanding of the formulation variables governing the MF-MDI product performance.

A 3D printed human upper respiratory tract model for particulate deposition profiling

Pulmonary route is the main route of drug delivery for patients with asthma and chronic obstructive pulmonary diseases, offering several advantages over the oral route. Determining the amount of drug deposited onto various parts of the respiratory tract allows for a good correlation to clinical efficacy of inhalation drug devices. However, current in vitro cascade impactors measure only the aerodynamic particle size distribution, which does not truly represent the in vivo deposition pattern in human respiratory tract. In this study, a human upper respiratory tract model was fabricated using a 3D printer and subsequently characterized for its dimensional accuracy, surface finishing and air leaking. The effects of using a spacer and/or various airflow rates were also investigated. To assess this in vitro model, the deposition pattern of a model drug, namely, salbutamol sulphate, was tested. The resultant deposition pattern of salbutamol sulphate from a metered dose inhaler at 15 L per minute with the spacer, showed no significant difference from that of a published radiological in vivo study performed in adult humans. In addition, it was also found that the deposition pattern of salbutamol at 35 L per minute was comparable to the results of another published study in human. This in vitro model, showing reasonable in vitro-in vivo correlation, may provide opportunities for personalized medicine in special populations or disease states.