Efficacy of low and high dose inhaled corticosteroid in smokers versus non-smokers with mild asthma.

BACKGROUND Cigarette smokers with asthma are insensitive to short term inhaled corticosteroid therapy, but efficacy when given for a longer duration at different doses is unknown. METHODS Ninety five individuals with mild asthma were recruited to a multicentre, randomised, double blind, parallel group study comparing inhaled beclomethasone in doses of 400 microg or 2000 microg daily for 12 weeks in smokers and non-smokers. The primary end point was the change in morning peak expiratory flow (PEF). Secondary end points included evening PEF, use of reliever inhaler, number of asthma exacerbations, spirometric parameters, and asthma control score. RESULTS After 12 weeks of inhaled beclomethasone there was a considerable difference between the morning PEF measurements of smokers and non-smokers with asthma (-18 (95% CI -35 to -1), adjusted p = 0.035). Among those receiving 400 microg daily there was a difference between the mean (95% CI) morning PEF (l/min) in smokers and non-smokers (-25 (95% CI -45 to -4), adjusted p = 0.019) and in the number of asthma exacerbations (6 v 1 in smokers and non-smokers, respectively, p = 0.007). These differences were reduced between smokers and non-smokers receiving 2000 microg inhaled beclomethasone daily. CONCLUSIONS Compared with non-smokers, smokers with mild persistent asthma are insensitive to the therapeutic effect of low dose inhaled corticosteroid treatment administered for a 12 week period. The disparity of the response between smokers and non-smokers appears to be reduced with high dose inhaled corticosteroid. These findings have important implications for the management of individuals with mild asthma who smoke.