Advancements in research on types of excipients of inhaled preparations

Pharmaceutical excipients are critical to the performance and safety of pulmonary inhaled formulations. This article reviews the research advances in key excipients of three dominating types of inhaled preparations: pressurized metered-dose inhalers, nebulizers, and dry powder inhalers. The first type contains propellants (becoming novel and environmentally friendly) that serve as the driving force, cosolvents/solubilizers (e.g., ethanol) that enhance drug solubility, and stabilizers (e.g., surfactants, antioxidants) that maintain physical and chemical stability. The second type-nebulizers-are solutions or suspension systems that rely on appropriate cosolvents and stabilizers to ensure the solubility, sterility and stability of drugs. Finally, dry powder inhalers, which require no propellants, depend on the properties of carrier excipients (e.g., lactose), the use of dispersion enhancers (e.g., L-leucine), and stabilizer systems to ensure stability of products. The research and development of excipients will become increasingly functional and intelligent. Advances in novel nano-excipients and nucleic acid delivery systems are expected to provide new solutions to the pulmonary delivery of macromolecular drugs.