An excellent free full text review by Paul O'Byrne.

What's new here: Did you know that formoterol is used as a first-line rescue inhaler, outside the U.S.? Formoterol has a steeper dose-response curve than salmeterol: repeated doses have an additive bronchodilator effect. The use of budesonide/formoterol as a combination maintenance AND rescue inhaler (added prn use during periods of increased symptoms) has been proven effective at preventing severe exacerbations in moderate to severe asthma and is standard care in European countries, although our black box warning against LABAs would make this an unorthodox treatment here. (The capsule formulation of formoterol monotherapy was intended to discourage its use as a rescue medicine.) The maintenance-plus-rescue approach reduces maintenance steroid dosing, oral steroid use, and improves lung function compared to usual U.S. care. (AJRCCM 2005)  (Lancet 2006)  (Resp Med 2007)

J Allergy Clin Immunol 2011;128:257-263. FREE FULL TEXT