Most of the beta-agonists used are racemic compounds that contain both the R and S enantiomers of the agonist. Much of the pharmacologic activity seems to reside in the R enantiomer, with the S thought to induce the negative side effects. Recently, the R enantiomer of both the short-acting agent albuterol (levalbuterol) and the long-acting agent formoterol (aformoterol) were approved for use in COPD. However, the cost effectiveness of these agents, in light of marginal observed clinical differences, remains controversial and needs further exploration.
Although the major action of beta2-agonists is relaxation of airway smooth muscles, they have also been shown to have several other potential effects. They seem to inhibit airway smooth muscle proliferation and inflammatory mediator release, as well as stimulation of mucociliary transport, cytoprotection of the mucosa, and attenuation of neutrophil recruitment and activation.
Multiple studies have demonstrated enhanced benefits of action when coadministered with inhaled anticholinergics and with corticosteroids.
The greatest single problem that persists in the acute phase is the under dosing of beta-agonists and the nonutilization of anticholinergics. Although only a small subset of patients respond to beta-agonists, a reasonable dose approaches continuous nebulization, as is seen in current asthma treatment.Keep in mind that with larger doses and continuous nebulization, elevated lactate levels are possible (see Workup).
-
Chronic obstructive pulmonary disease (COPD). Histopathology of chronic bronchitis showing hyperplasia of mucous glands and infiltration of the airway wall with inflammatory cells.
-
Chronic obstructive pulmonary disease (COPD). Histopathology of chronic bronchitis showing hyperplasia of mucous glands and infiltration of the airway wall with inflammatory cells (high-powered view).
-
Posteroanterior (PA) and lateral chest radiograph in a patient with severe chronic obstructive pulmonary disease (COPD). Hyperinflation, depressed diaphragms, increased retrosternal space, and hypovascularity of lung parenchyma is demonstrated.
-
Chronic obstructive pulmonary disease (COPD). A lung with emphysema shows increased anteroposterior (AP) diameter, increased retrosternal airspace, and flattened diaphragms on lateral chest radiograph.
-
Chronic obstructive pulmonary disease (COPD). A lung with emphysema shows increased anteroposterior (AP) diameter, increased retrosternal airspace, and flattened diaphragms on posteroanterior chest radiograph.
-
Subcutaneous emphysema and pneumothorax.
