[Steroid response after long-term treatment with oral N-acetylcysteine in patients with chronic obstructive...

The significance of long-term treatment with N-acetylcystein (NAC) for the steroid response on pulmonary function and general symptoms was investigated in patients with chronic bronchitis and moderate respiratory obstruction. All of the patients had received preliminary treatment with oral NAC in a dosage of 1,200 mg daily (Mucomyst Retard) or a placebo for 22 weeks in a double-blind design. After the conclusion of the long-term treatment but before the code was revealed, 37 non-allergic patients with irreversible respiratory obstruction participated in a follow-up investigation with 30 mg prednisone daily for 14 days. The peak flow was measured twice daily and the symptoms of bronchitis were registered by completion of 13 visual analogue scales. Pulmonary function was measured by means of spirometry on days 0, 7 and 14, respectively. In both of the treated groups, slight increase in the daily registered peak flow was found but no changes in the results of spirometry or the symptoms. Comparison between the groups revealed a significantly greater increase in the evening peak flow in the group which had received preliminary treatment with NAC. It is concluded that, in this investigation, no clinically relevant effect of long-term preliminary treatment with NAC on the results of a steroid test was observed in patients with chronic bronchitis and moderate respiratory obstruction.