Efficacy and safety of add-on sodium benzoate, a D-amino acid oxidase inhibitor, in treatment of schizophrenia: A systematic review and meta-analysis

Abstract

The role of sodium benzoate, an NMDA receptor enhancer, in schizophrenia has been evaluated in a few clinical trials, but results are contradictory and inconclusive. The present meta-analysis has evaluated the efficacy and safety of add-on sodium benzoate for the treatment of schizophrenia. After performing a literature search on MEDLINE/PubMed, Scopus, Cochrane databases and International Clinical Trial Registry Platform, reviewers assessed eligibility and extracted data from four relevant articles. PRISMA guidelines were followed in the selection, analysis, and reporting of findings. The random-effect model was used to estimate effect size. Quality assessment was done using the risk of bias assessment tool, and sensitivity analysis was done in case of high heterogeneity. Add-on sodium benzoate can improve positive symptoms of schizophrenia significantly (MD: -1.87; 95%CI: -3.25 to -0.48; p=0.008) but had no significant favourable effect on negative symptoms (p=0.84), general psychopathology (p=0.49), and total PANSS score (p=0.19) over the control. There was no significant improvement in GAF (p=0.43), CGI (p=0.58), cognitive function (p=0.46) and quality of life (p=0.73). Extrapyramidal symptoms were significantly higher (MD: 0.39; 95% CI:0.19-0.60; p=0.0002) in the sodium benzoate group in comparison to the control group; however, there was no significant difference in respect to other adverse events. Sodium benzoate can improve the positive symptoms of schizophrenia without any beneficial effect on other symptomatology, cognition, quality of life and functioning. Further studies are needed to evaluate long-term efficacy, safety and use in specific subgroups of patients.