Background: Patient evaluation of asthma severity and medication needs is mostly based on respiratory symptoms and may be influenced by changes in perception of bronchoconstriction-induced sensations. However, the influence of asthma medication on the ability to perceive symptoms is still to be documented. This study evaluated the effects of short-term and regular use of salmeterol on the perception of methacholine-induced bronchoconstriction (MIB) in subjects with mild asthma, using inhaled salbutamol on an "as required" basis (n=15), and in subjects with moderate asthma, using daily inhaled beclomethasone (mean daily dose, 640 microg; n=15) in addition to salbutamol to control their asthma.
Methods: Methacholine challenges (MC) were performed at entry into the study, and then before, 1, and 12 h following inhalation of 50 microg of salmeterol or a placebo, after a 15-day baseline period; and after 4 weeks of twice daily use of those treatments. The measurements were then repeated with the alternate treatment after a 15-day washout period. Finally, a last MC was performed after another 15-day washout period. For each MC, the perception score of bronchoconstriction-associated breathlessness at 20% fall in FEV1 (PS20) was evaluated on a modified Borg scale from 0 to 10.
Results: Subjects using regular beclomethasone had a higher baseline PS20 than those using only salbutamol (means: 3.06 0.06 and 2.01+/-0.07, p=0.0001). Short- and long-term use of salmeterol did not change significantly the PS20 compared with placebo (p>0.05) in either group (with or without corticosteroid). Although there were some intraindividual variations, mean PS20 did not vary significantly throughout the study.
Conclusion: These observations show that the perception of bronchoconstriction-associated breathlessness is not influenced by regular use of salmeterol. Patients using inhaled corticosteroids show a greater perception of MIB.