Attenuation of influenza-like symptomatology and improvement of cell-mediated immunity with long-term N-acetylcysteine treatment.
Level 2 - randomized trial
Multicenter, randomized, double-blind, placebo-controlled clinical trial
PubMed 9230243 · doi:10.1183/09031936.97.10071535
What was done
In a randomized, double-blind multicenter trial across 20 Italian centers, 262 subjects (78% aged >= 65 years, 62% with nonrespiratory chronic degenerative diseases; chronic respiratory patients excluded) were assigned to receive either placebo or N-acetylcysteine (NAC, 600 mg tablets twice daily) for 6 months. Outcomes included the incidence and severity of influenza-like episodes, seroconversion to A/H1N1 Singapore 6/86, and cell-mediated immunity shifts between anergy and normoergy.
What was found
Seroconversion rates to A/H1N1 virus were similar between groups, but only 25% of virus-infected participants receiving NAC developed symptomatic illness compared with 79% in the placebo group. NAC treatment also significantly decreased the frequency of influenza-like episodes, overall severity, and length of time confined to bed, with sharp reductions in both local and systemic symptoms. Evaluation of cell-mediated immunity demonstrated a progressive, significant shift from anergy to normoergy in the NAC group.
Why it matters
This study demonstrates that long-term prophylactic NAC can substantially reduce the clinical burden and symptom expression of influenza in high-risk older adults without preventing viral seroconversion, possibly via cell-mediated immune enhancement.
Limits
The abstract omits exact numerical values, standard deviations, and p-values for total episode frequency, symptom severity, and bed-rest duration. Results reflect a single winter season and one viral strain (A/H1N1), and individuals with chronic respiratory disease were excluded.
Cited by
- partial A clinical study showed that N-acetylcysteine (NAC) supplementation significantly reduced the rate of contracting influenza upon exposure compared to placebo, dropping infection from the high 70% range to around the high 20% range.