Little evidence supports the use of N-acetylcysteine ​​for chronic pain

Few studies support the use of N-acetylcysteine ​​(NAC) in the treatment of chronic pain, although some evidence suggests that NAC provides analgesic effects for some pain conditions, according to some meta-analyzes published in Pain Medicine.

Canadian researchers conducted a systematic review of studies discussing the use of NAC in the management of chronic pain in adults. A pooled meta-analysis was performed for 9 studies in which 863 patients with persistent or recurrent chronic pain conditions that lasted longer than 3 months participated.

Improvement in patient reported pain intensities was the primary result. Further results were adverse events (AEs), sleep effects and quality of life (QoL).

The 5 randomized controlled studies, 2 open non-comparative studies and 2 comparative studies included patients with sickle cell disease, complex regional pain syndrome, pelvic pain / endometriosis, rheumatoid arthritis, diabetic neuropathy or chronic neuropathic pain.

In the meta-analysis of 3 randomized controlled trials, the use of NAC was not associated with reduced pain intensities, which were assessed using visual analog scales or numerical rating scales (standardized mean difference) [SMD]-0.21; 95% CI, -0.33 to 0.75). In addition, treatment with NAC did not improve quality of life (SMD, 0.60; 95% CI, -4.44 to 5.64; P = 0.06), but according to a post-hoc sensitivity analysis (SMD, 0, 32) associated with a small significant effect on functional outcomes 95% CI, 0.07-0.57; P = 0.02). In one study, NAC and pregabalin had a significantly different effect on participants’ sleep (-5.60) than the participants in the control group (-3.91; P <0.001).

Reporting of side effects was inconsistent in all studies, and only 6 studies reported the type of side effects that patients experienced. Given the inconsistent nature of AE reporting, investigators wrote that they could not draw a conclusion about the safety of NAC in the treatment of chronic pain.

One limitation of this analysis was the inclusion of studies that showed “significant differences” in pain disorders, NAC doses, duration of treatment, and patient follow-up times.

The researchers added that it may be important to “investigate the role of NAC in chronic pain conditions that were not assessed in this meta-analysis,” including “where antioxidants can play a beneficial role, such as fibromyalgia, multiple sclerosis, osteoarthritis and chronic neuropathic pain. ”


Mohiuddin M, Pivetta B, Gilron I, Khan JS. Efficacy and safety of N-acetylcysteine ​​for the treatment of chronic pain in adults: a systematic review and meta-analysis. Pain Med. Published online February 9, 2021. doi: 10.1093 / pm / pnab042

This article originally appeared on Clinical Pain Advisor

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