ABSTRACT
The years since the early 1990s have seen many new scientific and engineering
developments related to the therapeutic inhalation technology, especially for
systemic delivery of drugs to the lungs. From novel inhaler to novel particle
design [1], these developments have focused largely on improving the efficiency
of the delivery of inhaled drugs to the lungs while limiting inhaler system user
complexity. In the most successful delivery systems, lung deposition efficiencies,
measured relative to the nominal dose of drug in the inhaler, have increased from
approximately 10% to 60% [1], and delivery reproducibility has improved as
well. Nevertheless, while early reports of inhaled insulin biovailability in
animals suggested numbers as high as 50% [2] and sustained pharmacodynamic
action following deposition in the lungs of several days [3], published results
from the most advanced human insulin trials [4] show relative biopotencies of
less than 5%, and no public data have yet emerged from the clinic to confirm the
feasibility of long-acting insulin delivery through the lungs. These circumstances
point to the need for continued scientific and technological innovation if inhaled
delivery of drugs for systemic application is to achieve widespread commercial
use.
