ABSTRACT
The primary functions of the respiratory system are air conducting, olfaction, and gas exchange. Gas exchange necessitates the large internal surface area of the lung, its extensive capillary bed, and the delicately structured pulmonary parenchyma. These features allow rapid absorption of pharmaceuticals and make inhalation delivery, for either local or systemic effect, an attractive option. Although the practice of inhalation therapy can be traced back many centuries, it was the invention of the metered dose inhaler (MDI) in the 1950s that provided the rst truly safe and effective means of inhalation dosing of pharmaceuticals. This led to a rapid expansion of inhalation medicine research, and asthma patients were the rst to benet with the availability of MDI salbutamol (beta agonist) in 1969. Dry powder inhalers (DPIs) and nebulizers followed, and compounds for inhalation are no longer restricted to small molecules; the rst protein DPI (insulin) for the treatment of diabetes became available in 2006 (Patton and Byron 2007), and there is growing interest in inhalation delivery of vaccines (Bennett et al. 2002).
