PubMed · 12030191
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A M Alpeter, R Belkengren, S Sapala. Pediatric management problems.. https://pubmed.ncbi.nlm.nih.gov/12030191/
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The humble origins of the propellant driven metered dose inhaler, as a response to a child's enquiry, initiated an industry which supplies approximately a half billion inhalers globally for the treatment of asthma. These inhalers fall into three major groups: nebulizers; propellant driven metered dose inhalers and dry powder inhalers. Each requires drug formulation, metering and device technology to be successful. In recent years there have been several new developments in the field including auxiliary systems to improve drug delivery from the device to the patient and new categories of device, notably single breath aqueous systems. As device technology improves and our understanding of the disease leads to new drugs the only barrier to therapy is the patient. Patient training and compliance will continue to be important factors in the success, or failure, of inhaled therapy and the role of health care professionals will depend on who sponsors their intervention.
Successful delivery of dry powder aerosols to the lung requires careful consideration of the powder production process, formulation and inhaler device. Newer production methods are emerging to prepare powders with desirable characteristics for inhalational administration. The conventional formulation approach of adding coarse lactose carriers to the drug to form binary powder systems to enhance powder flow and dispersion properties has been expanded to using finer carrier particles and hydrophobic materials, as well as ternary systems. Particle morphology and surface properties have also been explored to enhance powder performance. For the inhaler device, the new generation inhalers are designed to reduce or completely decouple the influence of air flow on the aerosol generation. Each of these determinants for powder aerosol delivery is reviewed with a strong focus on the patent literature that contains enormous information about the latest development in this field.
There are a multitude of formulation factors to consider when developing a pMDI. Evaluation of each of these variables has been performed over the years, but there has been an abundance of different approaches in the determination of the effects on device performance. Thus, although much is known about pMDI on the empirical level, a systematic approach has clearly been missing. With the ratification of the Montreal Protocol and the introduction of alternative propellant systems, the opportunity to establish relationships between different levels of testing, such as in vitro measurements and in vivo outcomes, and in vivo assessments and clinical outcomes, has arrived. This review outlines research efforts that have focused on the formulation of propellant-driven metered dose inhalers using alternative propellants. These formulation factors, including device characteristics, are reviewed with respect to the performance of MDIs.