Pharmacology of formoterol: an innovative bronchodilator.

Formoterol is an innovative, highly potent, beta-2 selective adrenoceptor agonist combining the clinical advantages of rapid onset of action with a duration of action in excess of 12 h. In vitro, formoterol is a potent airway smooth muscle relaxant with high intrinsic activity. Formoterol appears to be retained in airway smooth muscle for extended periods since its relaxant effect on human airway smooth muscle is resistant to repeated washing and formoterol displays "reassertion" of relaxation after washout of a beta-adrenoceptor antagonist. In addition to airway smooth muscle relaxation, formoterol inhibits a range of acute inflammatory processes in animal models including eosinophil activation and infiltration of the airways, microvascular leakage, and antigen-induced mediator release from human lung. Whether these non-airway smooth muscle effects may influence chronic airway inflammation in clinical asthma remains to be determined.