A Metered-dose Inhalers in the Modern Era: Technologies, Challenges, Industrial Insights and Future Directions

Abstract

Scope and Objective: Metered-dose inhalers (MDIs) remain the cornerstone of inhalation therapy for asthma and chronic obstructive pulmonary disease (COPD), offering a portable, efficient, and cost-effective means of delivering drugs directly to the lungs. The global MDI market is projected to grow from around US$26.22 billion in 2024 to about US$42.02 billion by 2035, representing an estimated CAGR of about 4.38%. This review aims to provide a comprehensive evaluation of the current state of MDI technologies, encompassing conventional pressurized MDIs, breath-actuated MDIs, and non-pressurized soft mist inhalers (SMIs). The discussion focuses on their mechanisms of operation, formulation strategies, technological innovations, clinical advantages, and inherent limitations. Additionally, the review highlights key industrial insights, regulatory challenges, and future trends driving innovation in inhalation drug delivery systems, with the goal of guiding future research and development in this evolving therapeutic field. Methodology: This review systematically compiles and analyses current scientific and industrial literature on MDIs, focusing on technological developments, formulation strategies, regulatory perspectives, and sustainability concerns. Sources from peer-reviewed journals, pharmacopeial standards, and regulatory guidance documents (FDA, EMA, and ICH) were critically evaluated to identify trends, challenges, and innovations influencing MDI design and performance. Particular emphasis was placed on device engineering, aerosol performance parameters, and the integration of quality-by-design (QbD) principles in product development and lifecycle management. Conclusions: MDIs continue to play a vital role in the management of Asthma and COPD; however, persistent issues such as patient misuse, adherence barriers, and the environmental impact of hydrofluoroalkane (HFA) propellants demand targeted innovation. Future progress in MDI technology requires a multidisciplinary approach combining advances in formulation science, sustainable propellant alternatives, and intuitive device design. Regulatory compliance must emphasize aerodynamic particle size distribution, emitted dose uniformity, extractable and leachable profiling, and robust in vitro–in vivo correlation (IVIVC). Harmonization with FDA and EMA guidelines through risk-based design control and QbD-driven development will be crucial in achieving safer, more effective, and environmentally responsible inhalation therapies.