N-acetylcysteine inhalation improved sputum rheology in chronic productive cough: Clinical application in two cases

This pilot study evaluated the effects of inhaled N-acetylcysteine (NAC) on sputum rheology in patients with chronic productive cough (CPC). Rheological measurements before and 30 min after inhalation were compared retrospectively in 16 outpatients receiving either NAC (n = 9) or bromhexine hydrochloride (BXH) (n = 7). NAC inhalation significantly reduced critical strain (γ_C), an indicator of sputum stringiness, from 2370 [1310-4390] % to 643 [389-700] % (median and interquartile range), with a significantly greater effect than BXH. This reduction was observed regardless of airway fungal colonization. In addition, two case reports, a 67-year-old man with bronchorrhea and a 79-year-old woman with refractory asthma, demonstrated improved quality-of-life scores evaluated with the Cough and Sputum Assessment Questionnaire (CASA-Q) and rheological improvement following 1-2 weeks of twice-daily NAC inhalation. These findings suggest that nebulized NAC may be a promising add-on therapy for refractory airway diseases characterized by high sputum stringiness (γ_C).