Mean FEV1 as a percentage of the predicted value on the first and last days of treatment in patients with asthma. Therapy consisted of salmeterol (40 µg twice daily), albuterol (180 µg four times a day), or placebo. Both beta agonists increased the FEV1, but the effect of a single dose lasted longer with salmeterol. The beneficial effect of both agents persisted at twelve weeks.
FEV1: forced expiratory volume in one second.
Redrawn from Pearlman DS, Chervinsky P, LaForce C, et al, N Engl J Med 1992; 327:1420.