N-Acetylcysteine (NAC) for Sinonasal Congestion and Phlegm

Evidence from Sinusitis Guidelines

The American Academy of Otolaryngology-Head and Neck Surgery states that guaifenesin is sometimes recommended to loosen nasal discharge, but there is no evidence regarding its effect on symptomatic relief of acute bacterial rhinosinusitis, and by extension, NAC is not mentioned as a treatment option for sinusitis in any major rhinosinusitis guideline 1, 2, 3
The European Position Paper on Rhinosinusitis reviewed mucoactive agents including NAC and concluded that data on the effect of muco-active agents in CRS are very limited and the quality of the data insufficient to advise on the use of muco-active agents in the treatment of patients with CRS 4

The Cystic Fibrosis Foundation concluded that evidence is insufficient to recommend for or against routinely providing N-acetylcysteine for the chronic use, with level of evidence poor and net benefit zero 5, 6
National asthma guidelines do not include NAC among recommended controller medications, according to the American Thoracic Society 7

Intranasal corticosteroids are the most effective option for nasal congestion in sinusitis, as recommended by the American Academy of Otolaryngology-Head and Neck Surgery and the American Academy of Allergy, Asthma, and Immunology 1, 3
Saline irrigation has a modest benefit for reducing symptoms and improving quality of life, particularly buffered hypertonic saline, as suggested by the American Academy of Otolaryngology-Head and Neck Surgery and the American Academy of Allergy, Asthma, and Immunology 1, 2, 8
Topical decongestants, such as xylometazoline, reduce congestion but should be limited to 3-5 consecutive days to avoid rebound congestion, as recommended by the American Academy of Otolaryngology-Head and Neck Surgery 1, 2
Oral decongestants, such as pseudoephedrine, may provide symptomatic relief, according to the American Academy of Otolaryngology-Head and Neck Surgery 1