N-Acetyl-cysteine against noise-induced temporary threshold shift in male workers.
Previous animal studies showed protective effects of antioxidant medicines against noise-induced hearing loss (NIHL). It is unclear whether antioxidants would protect humans from NIHL. We conducted a study to determine whether N-Acetyl-cysteine (NAC) protected men against noise-induced temporary threshold shift (TTS), and whether subgroups with genetic polymorphisms of glutathione S-transferase (GST) T1 and M1 responded to NAC differently. In this prospective, double-blind, crossover study, 53 male workers were randomly assigned to receive either NAC (1200 mg/day, 14 days) during the first period and placebo during the second period, or placebo during the first period and NAC during the second period. Dosing periods were separated by a washout period of 2 weeks. The hearing threshold changes were determined before and after each dosing period. Pre-shift hearing threshold for high frequencies was 19.1 dB. Daily exposure to noise ranged from 88.4 to 89.4 dB. The noise levels of different frequencies ranged from 80.0 to 89.4 dB with a peak-value at 4 kHz. NAC significantly reduced TTS (p = 0.03). When the participants were grouped by GST M1/T1 genotypes, the NAC effect was only significant among workers with null genotypes in both GSTM1 and GSTT1 (p = 0.004). NAC may prevent noise-induced TTS among occupationally noise-exposed men. The protective effect of NAC was more prominent in subjects with both GSTM1-null and GSTT1-null genotypes. (clinicaltrials.gov Identifier: NCT00552786).
Lin
Cheng-Yu
CY
Department of Otolaryngology, Tainan Hospital, Department of Health, West Central District, Tainan City 700, Taiwan.
Wu
Jiunn-Liang
JL
Shih
Tung-Sheng
TS
Tsai
Perng-Jy
PJ
Sun
Yih-Min
YM
Ma
Mi-Chia
MC
Guo
Yueliang L
YL
D000111:Acetylcysteine / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D000284:Administration, Oral; D000328:Adult; D001309:Auditory Threshold / Q000187:drug effects; D018592:Cross-Over Studies; D004311:Double-Blind Method; D016166:Free Radical Scavengers / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D005838:Genotype; D005982:Glutathione Transferase / Q000235:genetics; D006317:Hearing Loss, Noise-Induced / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009623:Noise, Occupational / Q000009:adverse effects*; D011110:Polymorphism, Genetic / Q000235:genetics; D011446:Prospective Studies; D016896:Treatment Outcome
D000111:Acetylcysteine; D016166:Free Radical Scavengers; D005982:Glutathione Transferase; C413545:glutathione S-transferase T1