Advances in soft mist inhalers

ABSTRACT

Introduction

Soft mist inhalers (SMIs) are propellant-free inhalers that utilize mechanical power to deliver single or multiple doses of inhalable drug aerosols in the form of a slow mist to patients. Compared to traditional inhalers, SMIs allow for a longer and slower release of aerosol with a smaller ballistic effect, leading to a limited loss in the oropharyngeal area, whilst requiring little coordination of actuation and inhalation by patients. Currently, the Respimat® is the only commercially available SMI, with several others in different stages of preclinical and clinical development.

Areas covered

The primary purpose of this review is to critically assess recent advances in SMIs for the delivery of inhaled therapeutics.

Expert opinion

Advanced particle formulations, such as nanoparticles which target specific areas of the lung, Biologics, such as vaccines, proteins, and antibodies (which are sensitive to aerosolization), are expected to be generally delivered by SMIs. Furthermore, repurposed drugs are expected to constitute a large share of future formulations to be delivered by SMIs. SMIs can also be employed for the delivery of formulations that target systemic diseases. Finally, digitalizing SMIs would improve patient adherence and provide clinicians with fundamental insights into patients’ treatment progress.

KEYWORDS:

• Soft mist inhaler
• aerosols
• inhalable formulations
• pulmonary drug delivery
• aqueous droplet inhaler
• non-pressurized metered-dose inhaler
• inhaled biologics

Article highlights

• Recent advancements in soft mist inhaler (SMI) device technologies and formulation design have enabled reproducible drug administration even for challenging inhaled therapies.

• Understanding the parameters that impact the performance of SMIs – including but not limited to spray velocity, size distribution and deposition, inhalation flow rate, and in vitro in vivo correlation are important to optimize the performance of existing SMIs.

• Formulation, device characteristics, and patient-dependent factors need to be considered while designing the next-generation SMI devices.

• As liquid inhaler that produces a slow-moving aerosol cloud to enter the respiratory tract, SMIs optimize drug delivery while minimizing inspiratory effort on the part of the patients. Further design developments, such as new more targeted nozzle designs, make them ideal for the delivery of biologic formulations.

Declaration of interest

N Buchmann and I Sibum are full-time employees of Resyca, manufacturer of the Pulmospray and PFSI Soft mist inhalers. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This review was supported by funding from ARC LP190100917.