The influence of formulation and spacer device on the in vitro performance of solution chlorofluorocarbon-free propellant-driven metered dose inhalers

Water Uptake by Evaporating pMDI Aerosol Prior to Inhalation Affects Both Regional and Total Deposition in the Respiratory System

As pulmonary drug deposition is a function of aerosol particle size distribution, it is critical that the dynamics of particle formation and maturation in pMDI sprays in the interim between generation and inhalation are fully understood. This paper presents an approach to measure the evaporative and condensational fluxes of volatile components and water from and to solution pMDI droplets following generation using a novel technique referred to as the Single Particle Electrodynamic Lung (SPEL). In doing so, evaporating aerosol droplets are shown capable of acting as condensation nuclei for water. Indeed, we show that the rapid vaporisation of volatile components from a volatile droplet is directly correlated to the volume of water taken up by condensation. Furthermore, a significant volume of water is shown to condense on droplets of a model pMDI formulation (hydrofluoroalkane (HFA), ethanol and glycerol) during evaporative droplet ageing, displaying a dramatic shift from a core composition of a volatile species to that of predominantly water (non-volatile glycerol remained in this case). This yields a droplet with a water activity of 0.98 at the instance of inhalation. The implications of these results on regional and total pulmonary drug deposition are explored using the International Commission of Radiological Protection (ICRP) deposition model, with an integrated semi-analytical treatment of hygroscopic growth. Through this, droplets with water activity of 0.98 upon inhalation are shown to produce markedly different dose deposition profiles to those with lower water activities at the point of inspiration.

Aerosol delivery via invasive ventilation: a narrative review

In comparison with spontaneously breathing non-intubated subjects, intubated, mechanically ventilated patients encounter various challenges, barriers, and opportunities in receiving medical aerosols. Since the introduction of mechanical ventilation as a part of modern critical care medicine during the middle of the last century, aerosolized drug delivery by jet nebulizers has become a common practice. However, early evidence suggested that aerosol generators differed in their efficacies, and the introduction of newer aerosol technology (metered dose inhalers, ultrasonic nebulizer, vibrating mesh nebulizers, and soft moist inhaler) into the ventilator circuit opened up the possibility of optimizing inhaled aerosol delivery during mechanical ventilation that could meet or exceed the delivery of the same aerosols in spontaneously breathing patients. This narrative review will catalogue the primary variables associated with this process and provide evidence to guide optimal aerosol delivery and dosing during mechanical ventilation. While gaps exist in relation to the appropriate aerosol drug dose, discrepancies in practice, and cost-effectiveness of the administered aerosol drugs, we also present areas for future research and practice. Clinical practice should expand to incorporate these techniques to improve the consistency of drug delivery and provide safer and more effective care for patients.

Core-shell particles for the dispersion of small polar drugs and biomolecules in hydrofluoroalkane propellants

PURPOSE

Demonstrate the applicability of a novel particle-based technology for the development of suspensions of small polar drugs and biomolecules in hydrofluoroalkane (HFA) propellants for pressurized metered-dose inhalers (pMDIs).

MATERIALS AND METHODS

Emulsification diffusion was used to prepare core-shell particles. The shell consisted of oligo(lactide) grafts attached onto a short chitosan backbone. The active drug was arrested within the particle core. Colloidal Probe Microscopy (CPM) was used to determine the cohesive forces between particles in a model HFA propellant. The aerosol characteristics of the formulations were determined using an Anderson Cascade Impactor (ACI). Cytotoxicity studies were performed on lung epithelial and alveolar type II cells.

RESULTS

CPM results indicate that particle cohesive forces in liquid HFA are significantly screened in the presence of the polymeric shell and correlate well with the physical stability of suspensions in propellant HFA. The proposed formulation showed little or no cytotoxic effects on both Calu-3 and A549 cells.

CONCLUSIONS

Core-shell particles with a shell containing the lactide moiety as the HFA-phile showed excellent dispersion stability and aerosol characteristics in HFA-based pMDIs. This is a general strategy that can be used for developing novel suspension pMDIs of both small polar drugs and large therapeutic molecules.