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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Date data sharing statement initially provided
Type of registration
Prospectively registered

Titles & IDs
Public title
Sodium benzoate in chronic schizophrenia – an open label, add-on safety and efficacy study
Scientific title
In people with treatment resistant schizophrenia, is sodium benzoate a tolerated and acceptable augmentation strategy: a phase Ib/II study.
Secondary ID [1] 285838 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Schizophrenia 294864 0
Treatment Resistance 294865 0
Condition category
Condition code
Mental Health 295123 295123 0 0

Study type
Description of intervention(s) / exposure
This is a 3 period, open-label study of Benzoic Acid (BA) added on to established antipsychotic medication in patients with chronic schizophrenia, who are symptomatic but stable.
The 3 periods are 1: baseline, with no study medication administered (2 weeks); 2: treatment with openlabel BA
500mg capsules, given twice daily (12 weeks); and 3: 4 weeks followup, where no further sodium benzoate is administered.

We will be dispensing pills weekly and asking participants to bring pills back to the next visit to monitor adherence.

Up to 24 participants will be enrolled. Because of its openlabel
design, participant numbers have been chosen pragmatically. Participants will be established on antipsychotic medication for >3 months prior to baseline. With the exception of clozapine, any other antipsychotic medication (oral or depot) is permitted.
Because this population are more likely to either be on multiple medications or medications with a significant side effect burden , previous studies in a non treatment resistant population will not be applicable: as this is a proof-of-concept trial, we have not included a control group.
Intervention code [1] 291706 0
Treatment: Drugs
Comparator / control treatment
Nil (Open Label trial)
Control group

Primary outcome [1] 294888 0
Positive and Negative Symptom Scale (PANSS)
Timepoint [1] 294888 0
12 week end point
Primary outcome [2] 294889 0
Scales for the Assessment of Negative Symptoms -- 20 item scale (SANS)
Timepoint [2] 294889 0
12 weeks
Primary outcome [3] 294890 0
Clinical Global Improvement (CGI)
Timepoint [3] 294890 0
12 weeks
Secondary outcome [1] 314287 0
MATRICS Consensus Cognitive Battery (MCCB)
Timepoint [1] 314287 0
12 weeks
Secondary outcome [2] 314288 0
Beck Hopelessness Scale
Timepoint [2] 314288 0
12 weeks
Secondary outcome [3] 314291 0
Reward Behaviour: Stimulus Chase Task (SCT) and Effort Expenditure for Rewards Task
Timepoint [3] 314291 0
12 weeks
Secondary outcome [4] 314292 0
Rosenberg Self-esteem Scale
Timepoint [4] 314292 0
12 weeks
Secondary outcome [5] 336192 0
Functional MRI prediction outcome
Timepoint [5] 336192 0
Prior treatment and end of treatment

Key inclusion criteria
1. A clinical diagnosis of Schizophrenia, confirmed by a structured diagnostic interview.
2. Have a body mass index between 18 and 35 (that is, not underweight or markedly overweight)
3. Have had no major change in their symptoms for three months.
4. Have moderate to severe current symptom
Minimum age
18 Years
Maximum age
65 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
1. You are pregnant or are intending to become pregnant.
2. Have a history of alcohol or drug dependance.
3. Have a history of epilepsy, head injury, or a neurological disorder.
4. If participating in the trial would place you at unacceptable risk.
5. If you are considered highly likely to not take any medications, as part of the study or not.

Study design
Purpose of the study
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
This is a pilot, open label trial of a novel use of Benzoic Acid. There is no blinding or allocation
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Not applicable
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?

Intervention assignment
Single group
Other design features
Pilot trial to ascertain

(a) acceptability of procedures in trial
(b) tolerability of Benzoic Acid.
(c) estimation of effect size for purposes of adequate powering a subsequent RCT.
(d) if functional neuroimaging can predict outcome.
Phase 1 / Phase 2
Type of endpoint(s)
Statistical methods / analysis
Descriptive data, with pre-post changes will be presented.

Recruitment status
Stopped early
Data analysis
No data analysis planned
Reason for early stopping/withdrawal
Participant recruitment difficulties
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment outside Australia
Country [1] 6842 0
New Zealand
State/province [1] 6842 0

Funding & Sponsors
Funding source category [1] 291152 0
Name [1] 291152 0
James Hume Memorial Fund
Department of Psychological Medicine
University of Otago
Address [1] 291152 0
University of Otago
P O Box 913, Dunedin 9054
New Zealand
Country [1] 291152 0
New Zealand
Primary sponsor type
Univeristy of Otago
P O Box 913, Dunedin 9054
New Zealand
New Zealand
Secondary sponsor category [1] 289830 0
Name [1] 289830 0
Address [1] 289830 0
Country [1] 289830 0

Ethics approval
Ethics application status
Ethics committee name [1] 292728 0
Central Health and Disability Committee
Ethics committee address [1] 292728 0
Ministry of Health
Ethics Department
Reception - Ground Floor
20 Aitken Street
Ethics committee country [1] 292728 0
New Zealand
Date submitted for ethics approval [1] 292728 0
Approval date [1] 292728 0
Ethics approval number [1] 292728 0

Brief summary
This study is to see if Benzoic acid is an acceptable add-on treatment for people who have Schizophrenia, have not responded to usual treatment, and have been stable for three months.

Benzoic acid is a food additive, It is frequently used in foods such as fizzy drinks, soy sauce, and preserved fish as a preservative, and has been regarded as safe for this purpose.

Benzoic acid has been tested as an add-on treatment in people with Schizophrenia in a clinical trial and it improved their symptoms when compared to placebo (an inactive tablet). No one has used this in people who do not respond to their usual medications.
Before we consider doing a large study to see if this medication will help, we want to see if it is truly safe and acceptable to people who may be asked to take it, particularly if they are taking other medications.
Trial website
Trial related presentations / publications
Public notes
Attachments [1] 419 419 0 0

Principal investigator
Name 53494 0
Dr Christopher Gale
Address 53494 0
Department of Psychological Medicine
Dunedin School of Medicine
University of Otago
P O Box 913
Dunedin 9054
Country 53494 0
New Zealand
Phone 53494 0
+64 21 707 193
Fax 53494 0
Email 53494 0
Contact person for public queries
Name 53495 0
Prof Christopher Gale
Address 53495 0
Department of Psychological Medicine
Dunedin School of Medicine
University of Otago
P O Box 913
Dunedin 9054
Country 53495 0
New Zealand
Phone 53495 0
+64 21 707 193
Fax 53495 0
Email 53495 0
Contact person for scientific queries
Name 53496 0
Dr Christopher Gale
Address 53496 0
Department of Psychological Medicine
Dunedin School of Medicine
University of Otago
P O Box 913
Dunedin 9054
Country 53496 0
New Zealand
Phone 53496 0
+64 21 707 193
Fax 53496 0
Email 53496 0

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No/undecided IPD sharing reason/comment
Not sufficient data to share.
What supporting documents are/will be available?
No other documents available
Summary results
No Results