100 Years of Drug Delivery to the Lungs

Inhalation therapy is one of the oldest approaches to the therapy of diseases of the respiratory tract. It is well recognised today that the most effective and safe means of treating the lungs is to deliver drugs directly to the airways. Surprisingly, the delivery of therapeutic aerosols has a rich history dating back more than 2,000 years to Ayurvedic medicine in India, but in many respects, the introduction of the first pressurised metered-dose inhaler (pMDI) in 1956 marked the beginning of the modern pharmaceutical aerosol industry. The pMDI was the first truly portable and convenient inhaler that effectively delivered drug to the lung and quickly gained widespread acceptance. Since 1956, the pharmaceutical aerosol industry has experienced dramatic growth. The signing of the Montreal Protocol in 1987 to reduce the use of CFCs as propellants for aerosols led to a surge in innovation that resulted in the diversification of inhaler technologies with significantly enhanced delivery efficiency, including modern pMDIs, dry powder inhalers and nebuliser systems. There is also great interest in tailoring particle size to deliver drugs to treat specific areas of the respiratory tract. One challenge that has been present since antiquity still exists, however, and that is ensuring that the patient has access to the medication and understands how to use it effectively. In this article, we will provide a summary of therapeutic aerosol delivery systems from ancient times to the present along with a look to the future.