Effects of tiotropium on lung function in current smokers and never smokers with bronchial asthma

The effects of tiotropium, an inhaled long-acting muscarinic antagonist, on lung function were investigated in current smokers and nonsmokers with asthma treated with inhaled corticosteroids (ICSs) and other asthma controllers: inhaled long-acting β₂ agonists, leukotriene receptor antagonists, and/or theophylline. We conducted a double-blind, placebo-controlled study of an inhaled single dose of tiotropium in 9 asthmatics currently smoking and 9 asthmatics who have never smoked in a crossover manner. Lung function was measured before and 1, 3, and 24 h after inhalation of 18 μg of tiotropium or a placebo. The primary outcome was a change in forced expiratory volume in 1 s (FEV₁) from the baseline, and the secondary outcomes were changes in peak expiratory flow rate (PEFR), V˙₅₀, and V˙₂₅. At baseline, asthmatics with and without a smoking history had a mean FEV₁ of 2590 ml and 2220 ml and were taking a mean dose of ICSs of 1208 and 1000 μg/day, respectively. The increase from the baseline FEV₁ was 169 ml and 105 ml higher at 3 h after tiotropium than after the placebo in current smokers and nonsmokers, respectively. PEFR, V˙₅₀, and V˙₂₅ were also significantly increased after tiotropium as compared with the placebo in both study groups. Changes in FEV₁ and PEFR tended to be greater in asthmatics currently smoking than in subjects who have never smoked, although there were no statistical differences at any time points. Tiotropium resulted in improved lung function and symptoms both in current smoker and nonsmoker asthmatics. These findings suggest that tiotropium will provide a new strategy for the treatment of bronchial asthma.