ABSTRACT
INTRODUCTION Recent advances in biotechnology have led to the availability of macromolecules such as peptides and proteins as therapeutic agents. Although oral administration would be most convenient for patients, intravenous, intramuscular, and subcutaneous injections are more practical for macromolecules, whose oral bioavailability is extremely low due to a large molecular size and high susceptibility to enzymes in the gastrointestinal tract. The lung is an attractive organ to administer proteins and peptides because of a large surface area, high permeability, low enzymatic activity, and noninvasive administration by inhalation (1).
