N-acetylcysteine as a treatment for substance use cravings: A meta-analysis

N-acetylcysteine (NAC) may serve as a novel pharmacotherapy for substance use and substance craving in individuals with substance use disorders (SUDs), possibly through its potential to regulate glutamate. Though prior meta-analyses generally support NAC's efficacy in reducing symptoms of craving, individual trials have found mixed results. The aims of this updated meta-analysis were to (1) examine the efficacy of NAC in treating symptoms of craving in individuals with SUD and (2) explore subgroup differences, risk of bias and publication bias across trials. Database searches of PubMed, Cochrane Library and ClinicalTrials.gov were conducted in June and July of 2023 to identify relevant randomized control trials (RCTs). The meta-analysis consisted of 9 trials which analysed data from a total of 623 participants. The most targeted substance in the clinical trials was alcohol (3/9; 33.3%), followed by tobacco (2/9; 22.2%) and multiple substances (2/9; 22.2%). Meta-analysis, subgroup analyses and leave-one-out analyses were conducted to examine the treatment effect on craving symptoms and adverse events (AEs). Risk of bias assessments, Egger's tests and funnel plot tests were conducted to examine the risk of bias and publication bias. NAC did not significantly outperform placebo in reducing symptoms of craving in the meta-analysis (SMD = 0.189, 95% CI = -0.015-0.393). Heterogeneity was very high in the meta-analysis (99.26%), indicating that findings may have been influenced by clinical or methodological differences in the study protocols. Additionally, results indicate that there may be publication bias present. Overall, our findings are contrary to those of prior meta-analyses, suggesting a limited impact of NAC on substance craving. However, the high heterogeneity and presence of publication bias identified warrants cautious interpretation of the meta-analytic outcomes.