ABSTRACT
Soft mist inhalers (SMIs) were developed to overcome limitations of pressurised metered-dose inhalers and dry powder inhalers. They are pocket-sized inhalers that use mechanical power to deliver single or multiple doses of inhalable aerosols from drug solutions to patients. Compared with traditional inhalers, SMIs deliver a higher fine particle fraction and allow for a longer release of aerosol with a lower ballistic force. This leads to an increased percentage of target-dose deposition in the lungs, with less loss in the oropharyngeal area, whilst requiring little co-ordination of actuation and inhalation by the patient. SMIs are resistant to environmental humidity and perform in a consistent and repeatable manner regardless of ambient temperatures or pressure. Currently, one device is commercially available (Respimat® Soft Mist™ Inhaler) and three are in clinical development (Aqueous Droplet Inhaler [ADI®], AERx Essence®, and Ecomyst®). Clinical data for Respimat confirm the safety and efficacy of the respective drug products in asthma and chronic obstructive pulmonary disease. Early clinical reports of the ADI show comparable lung deposition of tobramycin to that with a nebuliser. Human pharmacokinetics studies and lung deposition imaging data for the AERx Essence demonstrate that > 90% of the emitted aerosol dose deposits in the lung.
