Pulmonary drug delivery: novel pharmaceutical technologies breathe new life into the lungs

Pulmonary drug delivery is a developing technology in which medication is inhaled through the lungs and enters the bloodstream through the alveolar epithelium. Pulmonary drug delivery provides a noninvasive, alternative method to subcutaneous injection, and also intravenous injection. The delivery device plays a major role in the efficiency of pulmonary delivery, and great strides have been made in the development of new devices in recent years. The devices most commonly used for respiratory delivery, including nebulizers, metered-dose inhalers, and dry powder inhalers, can all be adapted for use with protein/peptide drugs. The choice of device will depend on the drug, the formulation, the site of action, and the pathophysiology of the lungs. While a great deal of recent research has focused on the development of novel devices, attention must now be paid to the formulation of these macromolecular drugs. The emphasis in this review will be on targeting of drugs by inhalation using carriers (such as liposomes, microspheres, microparticles, and nanoparticles) and ligands.