Oral Administration of the Antioxidant N-Acetylcysteine for Intervertebral Disc Degeneration: A Randomized, Placebo-Controlled, Double-Blind Study
Satoshi Suzuki, Daisuke Nakashima, Nobuyuki Fujita, Naoki Miyazaki, Noriyuki Ishida, Morio Matsumoto, Masaya Nakamura, Kota WatanabeStudy Design:
A randomized, placebo-controlled, double-blind trial.
Objective:
To investigate whether oral administration of the antioxidant N-acetylcysteine (NAC) can suppress intervertebral disc (IVD) degeneration associated with low back pain.
Summary of Background Data:
Although oxidative stress has been implicated in IVD degeneration, no oral pharmacological therapy has been established to suppress degenerative changes.
Methods:
Sixty patients, aged 20 to 64 years, presenting with low back pain accompanied by lumbar IVD degeneration of Pfirrmann grade ≥3 were included. Participants were randomly assigned to receive a placebo, NAC 1800 mg/day, or NAC 2700 mg/day for 24 weeks. The primary outcome was the changes in the mean full width at half maximum (mFWHM) averaged across lumbar IVDs, as measured using qspace imaging (QSI). Secondary exploratory outcomes included QSI parameters at each lumbar disc level and health-related quality of life, with subgroup analyses according to medication adherence rates.
Results:
The least squares mean change in mFWHM at 24 weeks was −99.0 (95% CI: −1027.6 to 829.7) in the placebo group, −995.6 (−1786.5 to −204.6) in the NAC 1800 mg group, and −656.2 (−1455.8 to 143.3) in the NAC 2700 mg group, showing no significant between-group difference. In subgroup analyses of participants with adherence rates ≥80%, the NAC 2700 mg group tended to show greater changes in selected secondary QSI parameters at specific disc levels and improvement in the SF-36 Bodily Pain subscale at four weeks. Adverse events were comparable across groups.
Conclusions:
The primary outcome was negative, indicating that oral NAC administration did not demonstrate a significant overall suppressive effect on IVD degeneration. However, exploratory secondary analyses suggested that high-dose NAC with high adherence might exert localized effects at specific lumbar levels, along with modest short-term pain relief.