This study evaluates 20% n-acetylcystine (NAC) in the treatment of moderate-to-severe asthma
that is complicated by mucus in the airway, as determined by CT imaging. The study is a
crossover design, which means that half the study participants will get 20% NAC in the first
7-day treatment period and placebo in the next 7-day treatment period; and the other half
will get placebo in the first 7-day treatment period and 20% NAC in the next 7-day treatment
period.