Delivery Options and Devices for Aerosolized Therapeutics

Although inhalation is one of the oldest modes of drug delivery, it is currently receiving renewed attention. Prior to 1987, aerosolized therapeutics were delivered via systems that relied on chlorofluorocarbon propellant systems. The subsequent ban on all nonmedical uses of these inert gases stimulated pharmaceutical companies to investigate other propellant systems. Two hydrofluoroalkanes were effective. However, in some instances, the change in propellant required reformulation of the drugs to be delivered. In some cases, bioequivalence could be achieved at lower doses with reduced toxicity. Pressurized metered-dose inhalers (pMDIs) have been used to deliver many types of inhaled therapeutics since the 1960s. Their major limitation is that drug delivery and effectiveness are affected by patient factors, including coordination difficulties and problems related to breathing and breath holding in patients with airway disease. Dry-powder inhalers are being developed to deliver powdered formulations of drugs such as bronchodilators and anti-inflammatory drugs for the treatment of asthma and COPD, and, eventually, proteins, peptides, recombinant products, and gene therapeutics. These devices have been proven to be as efficient as pMDIs in clinical trials. In some cases, they deliver a greater amount of the drug to the lungs. Percentages of the emitted dose deposited in the lungs range from 15 to 40% with the current generation of these devices. Finally, metered-dose liquid inhalers also are under development. Drug deposition in the lung with devices that are currently being tested ranges from 30 to 80% of the emitted dose. The choice of delivery system depends on the effective dose, drug deposition, patient ability, patient acceptance, and cost. Patient education in the correct use of each device is essential to maximize the therapeutic benefit.