Aerosol Therapy of Obstructive and Parenchymal Pulmonary Disease: Principles and Clinical Aspects

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Abstract
Aerosols are the mainstay of the pharmacotherapy of reversible airflow obstruction (RAO). They are available as a variety of bronchodilators and anti-inflammatory/anti-allergic drugs provided by several aerosol delivery systems, making ingested therapy almost unnecessary for control of asthma and COPD. Oral steroids are however, frequently required during exacerbations and in a minority of patients with very severe asthma. Metered dose inhalers (MDI) are the most convenient, efficient and inexpensive way to deliver therapeutic aerosols, however, many patients, particularly children, the elderly and handicapped are unable to manipulate these effectively, even after repeated instruction. Such patients benefit from powder inhalers or MDI add-on devices such as valved holding chambers that assure aerosol delivery and minimize local and systemic side effects. Future promising developments include sympathomimetic and anticholinergic bronchodilators with a 12 hour or greater duration of action, topically more active steroids in higher dose formulations with even less systemic side effects, and the use of liposomes to prolong the action of drugs at mucosal surfaces and decrease side effects. Preliminary results suggest that inhaled steroid aerosols may be useful for some patients with parenchymal lung disease, particularly sarcoidosis. Inhaled antitrypsin has been proposed for treating emphysema due to a deficiency of this enzyme, and there has also been a renewed interest in antibiotics delivered by the aerosol route, particularly in patients with bronchiectasis due to cystic fibrosis and immunosuppressed patients with opportunistic infections.