Long-Term Efficacy of Inhaled N-Acetylcysteine in Patients with Idiopathic Pulmonary Fibrosis

Background Inhalation of N-acetylcysteine (NAC) has been carried out in our department since 1994 for treating interstitial pneumonia such as idiopathic pulmonary fibrosis (IPF). In this study, the clinical efficacy and safety of long-term NAC inhalation monotherapy for IPF was investigated. Methods NAC inhalation was carried out in 23 of 34 cases diagnosed as IPF by surgical lung biopsy in our department between 1994 and 2008. The treatment was continued for one year or longer in 14 cases. In these 14 cases and in 11 cases without treatment, the clinical courses, prognosis, lung function (%FVC, %DLco, and %TLC), and changes in serum markers for interstitial pneumonia (KL-6 and SP-D) were examined. Results There were no significant differences in survival curves between the two groups. Acute exacerbation was observed in 4 of 14 cases (28.6%) receiving NAC inhalation. Compared with the results just before the beginning of NAC inhalation, Delta%FVC and Delta%DLco in the treated cases were -4.7% and -2.9% one year later and -4.0% and -5.8% two years later, respectively. In cases without treatment, Delta%FVC and Delta%DLco were -3.5% and +5.3% one year later and +0.2% and +1.0% two years later, respectively. Conclusion Since this study is an open case-control study in a single institute and the number of cases is not large, its use in evaluating the efficacy of NAC inhalation monotherapy is limited. In addition, the role of NAC inhalation in combination with a steroid, an immunosuppressive agent, and a new anti-fibrosis drug should also be investigated.