Pharmacokinetic considerations concerning the use of bronchodilators in the treatment of chronic obstructive pulmonary disease.

Bronchodilators are central to the symptomatic treatment of chronic obstructive pulmonary disease (COPD). Their pharmacodynamic aspects have been extensively described, but the pharmacokinetic profile of these drugs is much less well known. There are very few studies that describe the levels of drugs in the lung compartment following inhalation, and still very little is known about the relationships between drug levels in the lung and biological activity of bronchodilators. Areas covered: We review the existing evidence on the pharmacokinetics of bronchodilators, especially when administered to patients with COPD. Expert opinion: COPD does not substantially influence the pharmacokinetics of bronchodilators, although a modest signal, perhaps, exists for theophylline. We must highlight that plasma pharmacokinetics is suitable for establishing a systemic safety profile of inhaled bronchodilators but not their pulmonary efficacy profile because measurement of systemic blood values is neither at the site of action nor representative of transport to the site of action (the airways). However, there are large amounts of information from research in this field and recent advances with microdialysis and matrix-assisted laser desorption-ionization time-of-flight mass spectrometry to measure drugs in lung tissues that hopefully will lead to a better understanding of the pharmacokinetic/pharmacodynamic relationships for inhaled medicines.