Efficacy of N-acetylcysteine for treating dryness symptoms of Sjogren's disease: randomised placebo-controlled double-blind clinical study

Objective N-acetylcysteine (NAC) is used in Sjogren's disease (SjD) based on limited evidence. The aim of this study was to assess the efficacy of NAC for relieving dryness symptoms in SjD. Methods In this placebo-controlled double-blind trial, 60 adult SjD females (with low disease activity) were randomised to receive NAC (1,200 mg/day orally) or placebo. At baseline (D0), 30 days (D30) and 90 days (D90), all participants underwent the following evaluations: EULAR Sjogrens' Syndrome Patient Reported Index (ESSPRI), Ocular Surface Disease Index (OSDI), Xerostomia Inventory (XI), Leicester Cough Questionnaire (LCQ), unstimulated/stimulated salivary flow, Schirmer's test, and plasma levels of thiobarbituric acid reactive substances (TBARS), glutathione and NAC. Results At inclusion, both groups were balanced for age, ethnicity, disease duration, ESSPRI, OSDI, XI, Schirmers' test, salivary flow, ESSDAI and topical/systemic treatments (p>0.05). No significant differences were observed between NAC and placebo groups on D30 and D90 regarding ESSPRI, XI, OSDI, LCQ, Schirmer's test, stimulated salivary flow, ESSDAI and topical/systemic treatments (p>0.05). Unstimulated salivary flow was significantly higher in the placebo group on D90 (p=0.018). NAC blood concentrations were significantly higher in the NAC group on D30 (p=0.018) and D90 (p<0.001), however, no differences were found in TBARS and glutathione. Further analysis showed a decrease >= 1 in ESSPRI in the NAC compared with placebo group on D30 (p=0.045), a result not found on D90 (p=0.696). Conclusion NAC is recommended as a rescue therapy for SjD. However, our well-designed study provides novel evidence demonstrating its inefficacy for improving dryness symptoms or reducing oxidative stress. Clinicaltrials.gov-NCT04793646.