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Food preservative improves symptoms in schizophrenia

Research findings indicate that adjunctive sodium benzoate, a common food preservative, improved symptoms in patients with clozapine-resistant schizophrenia who did not see results with any other medications.

“Clozapine has been regarded as the last-line antipsychotic agent for refractory schizophrenia, though whether it is truly more efficacious than other competitors requires more rigorous studies,” Chieh-Hsin Lin, MD, PhD, department of psychiatry, Chang Gung Memorial Hospital, Taiwan, and colleagues wrote in Biological Psychiatry. “Sodium benzoate adjuvant therapy at 1 g/day has shown efficacy in improving both the clinical and cognitive symptoms of patients with chronic schizophrenia. However, whether sodium benzoate can improve clozapine-resistant schizophrenia is unknown.”

According to the researchers, inhibiting D-amino acid oxidase may benefit patients receiving antipsychotics. They conducted a randomized, double-blind, placebo-controlled study to evaluate the safety and efficacy of sodium benzoate, a D-amino oxidase inhibitor, in 60 patients with schizophrenia who had poor response to clozapine.

Participants already taking clozapine were randomly assigned to receive either add-on treatment of 1 g per day sodium benzoate, 2 g per day sodium benzoate or placebo for 6 weeks. Lin and colleagues measured the total score on the Positive and Negative Syndrome Scale (PANSS), Scale for the Assessment of Negative Symptoms (SANS), Quality of Life Scale and Global Assessment of Functioning as well as adverse effects and cognitive function.

After 6 weeks of treatment, the participants who received sodium benzoate showed greater improvement in SANS scores compared to placebo throughout the study. Patients receiving 2 g per day of sodium benzoate also experienced greater improvement than placebo in PANSS-total score, PANSS-positive score and Quality of Life Scale. Sodium benzoate had no effect on cognitive function but was well-tolerated without serious adverse effects. Furthermore, Lin and colleagues observed changes in the antioxidant catalase that were different between the three groups and related to the improvement of PANSS-total score and PANSS-positive score in those taking sodium benzoate.

According to the researchers, these findings indicate that sodium benzoate may benefit clinical symptoms and quality of life in patients with clozapine-resistant schizophrenia.

“If the finding can be confirmed in the future larger-sized studies, this approach of applying a [D-amino acid oxidase] inhibitor will bring hope for the patients who are resistant to clozapine treatment,” Lin and colleagues wrote. “For future studies and potentially clinical use, measurement of benzoic acid levels in peripheral blood may be helpful for determining the optimal dose of treatment.” – by Savannah Demko

Disclosures: The authors report no relevant financial disclosures.