Treatment of military acoustic accidents with N-Acetyl-L-cysteine (NAC)

Int J Audiol. 2019 Mar;58(3):151-157. doi: 10.1080/14992027.2018.1543961. Epub 2019 Jan 17.


Objective: To study if the antioxidant (AO) N-Acetyl-L-cysteine (NAC) reduces the risk of hearing loss after acoustic accidents in humans.

Design: A retrospective, observational study.

Study sample: Personnel of the Swedish Armed Forces (SAF) exposed to military acoustic accidents during a 5 year period. Included in the study were 221 cases (mean age: 22.9 years). Most of the exposures, 84%, were weapon related. NAC (400 mg) was given directly after the accident in 146 cases; 75 had not received NAC.

Results: The prevalence of hearing thresholds ≥25 dB HL, and the incidence of threshold shifts ≥10 dB, was lower in the NAC group than in the non-NAC group directly after the noise exposure. The deterioration was temporary and not discernable a long time after the accident. The difference was most pronounced in the right ear. The risk reduction to get a temporary hearing loss (TTS), affecting one or both ears was 39% (significant) in the NAC group.

Conclusions: The study has demonstrated a significant reduction of the incidence of TTS by the use of NAC. Since cases of both permanent hearing loss (PTS) and noise-induced tinnitus are recruited from cases with TTS, the demonstrated risk reduction indicates a positive effect of NAC.

Keywords: Acoustic trauma; Swedish Armed Forces (SAF); antioxidant (AO); noise-induced hearing loss (NIHL); permanent threshold shift (PTS); relative risk (RR); temporary threshold shift (TTS).

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcysteine / therapeutic use*
  • Adolescent
  • Adult
  • Female
  • Free Radical Scavengers / therapeutic use*
  • Hearing Loss, Noise-Induced / drug therapy*
  • Humans
  • Male
  • Military Personnel
  • Retrospective Studies
  • Young Adult


  • Free Radical Scavengers
  • Acetylcysteine