Abstract

Drugs used in the management of respiratory disorders are usually administered via the lungs or pulmonary route. Additionally, administration of drugs into the lungs can be a means of getting drugs into systemic circulation. For systemic effects, drugs have to be absorbed from the lungs into the bloodstream. Processes that aid drug absorption include transcytosis, paracellular transport, and/or absorption through large transitory pores in the alveolar epithelium. Metabolism of drugs in the lungs differs significantly from what pertains in the liver and intestines. The levels of expression of enzymes in the lungs are generally low, thus, xenobiotic clearance is also low. These pharmacokinetic characteristics of the lungs are relevant determinants in drug design and delivery. Recent reports suggest the use of lung drug delivery systems for insulins, growth hormones, corticosteroids, and antibiotics. These novel lung drug delivery systems may prove essential in the management of several diseases.