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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
Neural pathways in problem gambling: Brain function after using Naltrexone for problem gambling.
Scientific title
A pilot for regular Naltrexone (Revia Tablets, 25-150mg per day) dosing of 9 Problem Gamblers for 8-12 weeks assessing their neural changes (pre- and post Naltrexone dosing) using function magnetic resonance imaging.
Secondary ID [1] 262200 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Problem Gambling 286217 0
Condition category
Condition code
Mental Health 286433 286433 0 0

Study type
Description of intervention(s) / exposure
Regular Naltrexone dosing. Initially, participants will be given seven 25mg oral Naltrexone (ReVia; Bristol-Myers Squib) half tablets at intake (to be taken one a day for seven days). The full dosing regimen will begin if no toxicity issues are observed during the previous week and consists of 7 50mg tablets (one per day for seven days). If gambling urges continue dosages can be stepped up in weekly increments to 21 oral 50mg tablets per week (maximum of three 50mg tablets per day). Therefore, daily dosages can range between 25mg to 150mg. The treatment duration is 8-12 weeks depending on efficacy of medication (12 weeks of treatment is scheduled but can be reduced to 8 if significant improvements have been observed).
Intervention code [1] 284620 0
Treatment: Drugs
Comparator / control treatment
Control group

Primary outcome [1] 286878 0
Gambling behaviour. This will be measured using the timeline followback questionnaire.
Timepoint [1] 286878 0
intake, weekly, post treatment
Secondary outcome [1] 296896 0
Neural functioning; impulsivity, inhibition, gambling urges. The level of neural activation to three measures of psychological traits associated with problem gambling will be measured using functional magnetic resonance imaging (blood oxygenation level dependent signal change) and correlated with task events and behavioural responses. Impulsivity will be measured using a delay discounting task, inhibition will be measured using the STROOP task, and gambling urges will be measured by a gambling stimuli task.
Timepoint [1] 296896 0
intake, post treatment
Secondary outcome [2] 296897 0
Alcohol use. Weekly breath sample and Timeline Follow back questionnaire.
Timepoint [2] 296897 0
intake, weekly, post treatment
Secondary outcome [3] 296909 0
Liver Toxicity. Blood Liver Tests
Timepoint [3] 296909 0
Intake, mid-trial, post treatment

Key inclusion criteria
18-70 years of age.
Provide written consent.
Evidence of Problem Gambling (PGSI).
Seeking treatment for problem gambling.
Primarily Electronic Gaming Machine (EGM) gamblers.
English speaking.
Minimum age
18 Years
Maximum age
70 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Evidence of a current significant medical illness, psychiatric or neurological disorder (except for medically unmanaged anxiety, mood, and antisocial personality disorders) as indicated by responses to the MINI or semi-structured life histories questionnaire (e.g. medical, psychiatric, and drug histories).
Positive urine specimen to drugs of abuse.
History of a traumatic brain injury or loss of consciousness (10 minutes or more).
History of evidence of claustrophobia
Failure to follow laboratory or study procedures.
Left handed.
Any condition or circumstance that prohibit imaging sessions such as metal implants.
Contraindications to clinical doses of Naltrexone (e.g. currently using opioid analgesics, are opioid dependent, have acute hepatitis, hypersensitivity to Naltrexone, liver/kidney hypertoxicty, or hepatotoxicity).
History or evidence of allergic reactions to Naltrexone administration (i.e., rash, itching/swelling, severe dizziness, trouble breathing)/
Concurrent use of additional alcohol dependence medication e.g. disulfiram.
Evidence of current illicit opioid use
Use of medications containing opioids/opiates
Uncorrected visual impairment
Evidence of brain abnormalities from structural scans
Evidence of heart, liver or kidney failure. We will test for liver function in two ways. First, creatinine levels will be assessed to measure general liver function, where levels outside the normal range (Males: 0.6 – 1.2 mg/dl, Females: 0.5 – 1.1 mg/dl) will exclude participation. Second, we will test for aminotransferase liver enzymes in the blood, specifically; aspirate aminotransferase (AST) and alanine aminotransferase (ALT) in a selective blood metabolic panel. Scores outside the normal range for AST (Males: 15 – 40 U/L, Females: 13 – 35 U/L) or ALT (Males; 10 – 40, Females: 7 – 35) will exclude participation. The definition of heart failure we will use is the inability of the heart to supply sufficient blood flow to meet the needs of the body (Medterms.com, 2011), as evidenced in a clinical interview and physical examination by our physicians.

Study design
Purpose of the study
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Potential treatment participants will be recruited from patients who attend the Addiction Medicines Clinic at St Vincent’s Hospital. Local general practitioners will also be informed of the study and interested patients will be directed to contact the Addiction Clinic. Those patients wishing to join the study will complete a pre-screening questionnaire which the chief investigator will review. Those meeting our initial criteria (i.e., 18 – 70 years, evidence of problem gambling, right handed, no current unmanaged medical or psychological issues, no history of brain injury, no metal implants, no current use of alcohol dependence medication, no current use of opioid analgesics) will be contacted and asked to attend an enrolment session at St Vincent’s Addiction Medicines Clinic.

We will obtain a range of demographic, contact information (including alternative contact numbers, addresses and people), verification of identity, medical, and cognitive data from participants to assess for eligibility (e.g. MINI, PGSI, etc.). In addition, the MRI safety screening form will be administered to check for contraindications for scanning, whilst absence from recent substance use (e.g. cocaine, marijuana, methamphetamine, etc.) will be assessed using a urine specimen from each participant and assessed by St Vincent’s Laboratory for evidence of opiates, benzodiazepines, cannabis, and amphetamines. To assess for possible hepatotoxicity medical staff will draw blood and conduct liver function tests (also assessed by St Vincent’s Laboratory). Research staff will ask participants to blow into a breath alcohol analyser (Alcolizer HH1/HH2 personal Breath Tester, manufactured by Drivecheck Australia 2000 Pty Ltd) to test for recent alcohol consumption. Once eligibility has been determined the consent process starts. For those who are ineligible for this study they will be directed to free Gambler’s Help Services.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
N/A. Sequential recruitment methods; no randomised allocation as their is only one group.
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?

Intervention assignment
Single group
Other design features
The methodology we will use is a pre- and post-test design comparing changes in gambling dependence. Participation will last approximately 10-14 weeks: 8-12 weeks for treatment, and 2 weeks of assessments (one week prior to treatment and one week post treatment). There will be one group; an experimental group consisting of 9 people. The participant schedule is as follows:
1. Recruitment: Rescreening of potential participants using a short questionnaire completed in the clinic. Approximately 5 minutes
2. Enrolment: Consent process and forms completed and signed. Initial psychological assessments administered (i.e., MINI), breath sample, blood sample and urine specimen supplied at clinic. Approximately 1 hour.
3. Intake: Baseline psychometric measures taken at clinic. Approximately 1.5 hours. Brain scan at St Vincent’s Hospital Melbourne MRI. Approximately 1.5 hours (Enrolment and Intake will occur in the same session).
4. Treatment: Weekly dispensing of 7- day supply of oral Naltrexone tablets (Initially 7 half tablets per week, one a day; maximum 21 full tablets, three per day). This will take approximately 8-12 weeks (8-12 visits) and last approximately 5 minutes (40 minutes to 1 hour total). Weekly breath sample and Timeline Follow-back questionnaire taking approximately 25 minutes (4 -6 hours in total). Mid-trial: Blood liver function tests. Blood draw during weekly assessments. Delay-Discounting and Process of change administered outside scanner. Approximately 15 minutes
5. Post-Treatment: Psychological assessments, approximately 1.5 hours. TimeLine Follow-back, blood sample and breath sample at clinic, approximately 30 minutes. Brain scan at St Vincent’s Hospital Melbourne MRI. Approximately 1.5 hours.

Total Visits: 11 -17 (per participant)
Total Time: 13 hours – 15 hours (per participant)
Type of endpoint(s)
Statistical methods / analysis

Recruitment status
Reason for early stopping/withdrawal
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)

Funding & Sponsors
Funding source category [1] 285034 0
Name [1] 285034 0
Melbourne Research Office, University of Melbourne
Address [1] 285034 0
Level 5, Alan Gilbert Building,
161 Barry Street (Cnr Grattan Street),
Carlton,Victoria 3053
Country [1] 285034 0
Funding source category [2] 285035 0
Name [2] 285035 0
Problem Gambling Research and Treatment Centre, University of Melbourne
Address [2] 285035 0
100 Leicester Street,
Victoria 3010
Country [2] 285035 0
Primary sponsor type
Problem Gambling Research and Treatment Centre, University of Melbourne
100 Leicester Street,
Carlton, Victoria 3010
Secondary sponsor category [1] 283897 0
Name [1] 283897 0
Addictions Medicine, St Vincent's Hospital Melbourne
Address [1] 283897 0
Addictions Medicine,
38 Fitzroy Street,
Victoria 3065
Country [1] 283897 0
Other collaborator category [1] 260698 0
Name [1] 260698 0
Neurology, St Vincent's Hospital Melbourne
Address [1] 260698 0
41 Victoria Parade,
Victoria 3065
Country [1] 260698 0

Ethics approval
Ethics application status
Ethics committee name [1] 287039 0
Human Research Ethics Committee - D (Drug/Device)
Ethics committee address [1] 287039 0
Research Governance Unit,
Level 5, Mary Aikenhead Building,
27 Victoria Parade,
Victoria 3065
Ethics committee country [1] 287039 0
Date submitted for ethics approval [1] 287039 0
Approval date [1] 287039 0
Ethics approval number [1] 287039 0

Brief summary
We propose to examine the effects of regular Naltrexone dosing as an off-label treatment for problem gamblers. We plan to examine the neural activation when we present gambling stimuli, are asked to make self-controlled or impulsive hypothetical choices and when subjects have to inhibit a learned response. Participants will be tested pre and post treatment and correlate these responses with the urge to gamble and self-reported gambling behaviour. By examining these relationships, specifically the change in neurological functioning, we hope to find the neural correlates to measures of problem gambling. Investigating these issues will assist in the analysis of a putative common neurological basis between gambling and alcoholism and hopefully advance both treatments
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 32624 0
A/Prof Darren R. Christensen
Address 32624 0
Faculty of Health Sciences,
University of Lethbridge,
4401 University Drive,
Alberta, T1K3M4
Country 32624 0
Phone 32624 0
+1 403-329-5124
Fax 32624 0
Email 32624 0
Contact person for public queries
Name 15871 0
A/Prof Darren R. Christensen
Address 15871 0
Faculty of Health Sciences,
University of Lethbridge,
4401 University Drive
Alberta, T1K3M4
Country 15871 0
Phone 15871 0
+1 403-329-5124
Fax 15871 0
Email 15871 0
Contact person for scientific queries
Name 6799 0
A/Prof Darren R. Christensen
Address 6799 0
Faculty of Health Sciences,
University of Lethbridge,
4401 University Drive
Alberta, T1K3M4
Country 6799 0
Phone 6799 0
+1 403-329-5124
Fax 6799 0
Email 6799 0

No information has been provided regarding IPD availability
Summary results
No Results