Salmeterol response is not affected by β2-adrenergic receptor genotype in subjects with persistent asthma

BackgroundRecent studies suggest that there might be an association between albuterol use and worsening asthma in patients homozygous for arginine (Arg/Arg) at codon 16 of the β-receptor. However, it is not known whether similar responses occur in Arg/Arg patients receiving long-acting β2-agonists.ObjectiveWe sought to evaluate the effects of variation in the β2-adrenergic receptor gene (ADRB2) on clinical response to salmeterol administered with fluticasone propionate.MethodsSubjects (n = 183) currently receiving short-acting β2-agonists were randomized to twice-daily therapy with salmeterol, 50 μg, administered with fluticasone propionate, 100 μg, in a single inhaler or daily therapy with montelukast for 12 weeks, followed by a 2- to 4-day run-out period.ResultsThere was sustained and significant improvement (P < .001) over baseline in all measures of asthma control in subjects receiving salmeterol, regardless of Arg16Gly genotype. Morning peak expiratory flow in subjects with the Arg/Arg genotype showed 89.0 ± 16.1 L/min improvement over baseline compared with 93.7 ± 12.7 L/min for Gly/Gly subjects and 92.5 ± 11.9 L/min for Arg/Gly subjects. Pairwise changes were similar for Arg/Arg compared with Gly/Gly or Arg/Gly genotypes (estimated differences, 4.7 L/min and 3.5 L/min, respectively). Responses did not appear to be modified by haplotype pairs. During the run-out period, all subjects had predictable and similar decreases in measures of asthma control, with no differences between genotypes.ConclusionResponse to salmeterol does not vary between ADRB2 genotypes after chronic dosing with an inhaled corticosteroid.Clinical implicationsAnalyses from this study indicate that genetic polymorphisms leading to Arg16Gly sequence changes within the β2-adrenergic receptor do not affect patients' responses to recommended asthma therapy with salmeterol and fluticasone propionate.