Historically, drug delivery technologies have been used to extend the duration of effect, or to speed the onset of action, of drugs or to improve the convenience of their administration. Today the role of drug delivery technology has been expanded to include improving the efficiency and specificity with which drugs can be delivered to their target organs or systems. Inhalational drug therapy, in which drugs are delivered to the lungs in the form of an aerosol, is one example. Because inhaled drugs are absorbed directly into the bloodstream, the development of pulmonary methods of drug delivery to replace oral methods avoids exposure of the drug to the harsh gastrointestinal environment, minimizing gastroin-testinal problems such as low solubility, low permeability, drug irritability, unwanted metabolites, and dosing uncertainty caused by meals of varied composition. Because they are delivered directly to diseased lungs, certain inhalable antibiotics may be more effective than oral or injectable antibiotics for treating lung infections.