A Phase 2 interventional study of Cannabidiol capsules and Naltrexone (drug) in Alcohol Addiction and Alcoholism, sponsored by Central Institute of Mental Health, Mannheim. Recruiting at 2 sites in Germany. Open to participants aged 18 Years to 70 Years. Per ClinicalTrials.gov, last updated 2026-02-03.
Sponsored by Central Institute of Mental Health, Mannheim · Phase 2, Interventional, and Treatment
Alcohol addiction (AD) is a chronic relapsing disorder with currently limited pharmacological treatment options. Alcohol craving, a hallmark symptom of AD that drives relapse in patients, is only insufficiently treated by existing medication. One promising new compound for the treatment of alcohol craving in AD is Cannabidiol (CBD), which showed beneficial effects on alcohol craving in preliminary clinical studies. Additionally, CBD seems to be a particularly promising candidate for enhancing the effects of established medication, specifically Naltrexone (NTX), an opioid-antagonist, which is approved for AD treatment, due to the synergistic effects of the combination of Cannabidiol plus Naltrexone on alcohol consumption that were shown by preclinical studies. The proposed three-armed, 1:1:1 randomized, double-blind, placebo-controlled parallel group, multicentric phase II trial seeks to test the putative synergistic effects of combined CBD (800mg) + oral NTX (50mg) against CBD (1200mg) + oral NTX (50mg) against Placebo + oral NTX (50mg) on alcohol craving (primary outcome) in male and female patients with AD that suffer from high alcohol craving. The trial seeks to test the effects of the innovative combination of CBD plus NTX against Placebo plus NTX on alcohol craving over a 14-day treatment period, which is embedded in a standardized addiction treatment program according to current treatment guidelines, in order to estimate the added value of treatment with CBD on alcohol craving. Quality of life and neurobiological and biochemical markers for craving will serve as secondary outcomes, because they show strong associations to treatment outcome and relapse risk. Collection and analysis of follow-up data (28 days, 42 days, 105 days, 196 days) will be performed to determine whether treatment effects relate to patient outcome.
1,674 studies on the registry are indexed under Alcoholism; 331 are open to participants now.
This study's planned enrollment of 150 is above the median of 88 across 1,428 interventional studies indexed under Alcoholism.
Browse Alcoholism studies →Central Institute of Mental Health, Mannheim is the lead sponsor of 60 studies on the registry; 9 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ALT and AST (liver enzymes)
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ULN (upper limit of normal)
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Bilirubin
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Excipients
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
All patients will receive 50mg Naltrexone daily (NTX, oral tablet) in the course of standard in-patient treatment. In the experimental group of trial arm 1, patients will receive a dose of 800mg Cannabidiol (CBD) daily over the course of 14 days during in-patient treatment.
Drug: Cannabidiol capsules · Drug: Naltrexone (drug)
All patients will receive 50mg Naltrexone daily (NTX, oral tablet) in the course of standard in-patient treatment. In the experimental group of trial arm 2, patients will receive a dose of 1200mg Cannabidiol (CBD) daily over the course of 14 days during in-patient treatment.
Drug: Cannabidiol capsules · Drug: Naltrexone (drug)
All patients will receive 50mg Naltrexone daily (NTX, oral tablet) in the course of standard in-patient treatment. In the comparator group of trial arm 3, patients will receive placebo capsules daily over the course of 14 days during in-patient treatment.
Drug: Naltrexone (drug) · Drug: Placebo
800mg (trial arm 1) or 1200mg (trial arm 2) Cannabidiol capsules will be administered daily over the course of 14 days.
All participants will receive 50mg Naltrexone daily as oral tablet throughout the study.
Placebo capsules matching the cannabidiol capsules will be administered daily.
Obsessive Compulsive Drinking Scale (OCDS-G)
The alcohol craving will be assessed at separate time points before and after Cannabidiol administration using the Obsessive Compulsive Drinking Scale. The Obsessive Compulsive Drinking Scale consists of 14 items, each rated on a 5-point Likert scale (0-4), resulting in scores from 0 to 40, with higher scores indicating higher craving.
Time frame: The difference of alcohol craving between baseline (visit 2) and 14 days after the first treatment visit (visit 5) will serve as primary endpoint.
Obsessive Compulsive Drinking Scale (OCDS-G)
The alcohol craving will be assessed at separate time points before and after Cannabidiol administration using the Obsessive Compulsive Drinking Scale. The Obsessive Compulsive Drinking Scale consists of 14 items, each rated on a 5-point Likert scale (0-4), resulting in scores from 0 to 40, with higher scores indicating higher craving.
Time frame: Differences from baseline (visit 2, day -2) of Obsessive Compulsive Drinking Scale craving scores to visits 4 (day 7, i.e., 7 days after the first treatment visit) and during follow up visits 6 (day 28), 7 (day 42), 8 (day 105), 9 (day 196)
Subjective quality of life index
Quality of life will be assessed using the World Health Organization Quality of life questionnaire (WHO-QOL-BREF) scores at separate time points before and after Cannabidiol administration. The World Health Organization Quality of life questionnaire is an instrument that can assess patients' global health status independently of disease across 4 health domains and consists of 26 items rated on a 5-point Likert scale (1-5). To calculate the score, items 3, 4, 26 have to be inverted. Scores for each domain (Physical Health, Psychological Health, Social Relationships, Environment) are calculated, that range from 4 to 20. Higher scores indicate better quality of life, with the overall score reflecting a person's general well-being.
Time frame: Differences from baseline (visit 2, day -2) of Quality of life (WHO-QOL-BREF scores) to end of treatment (visit 5, day 14) and follow up visits 6 (day 28), 7 (day 42), 8 (day 105), 9 (day 196).
Beck Depression Inventory (BDI-II)
The depressive symptoms will be assessed at separate time points before and after Cannabidiol administration using the Beck Depression Inventory (BDI-II). The Beck Depression Inventory (BDI-II) is a 21-item self-rating inventory that measures characteristic attitudes and symptoms of depression. Each Item is rated on a 4-point Likert scale (0-3). The total score ranges from 0 to 63, with higher scores indicating more severe depressive symptoms.
Time frame: Difference from baseline (visit 2, day -2) of depressive symptoms to end of treatment (visit 5, day 14)
State Trait Anxiety Inventory (STAI)
The state and trait anxiety will be assessed at separate time points before and after Cannabidiol administration using the State Trait Anxiety Inventory. The State Trait Anxiety Inventory (STAI) is a 20-item self-report questionnaire that assesses state anxiety and trait anxiety via two subscales: the State Anxiety Scale (STAI-S) and the Trait Anxiety Scale (STAI-T), each consisting of 20 items. Each item is rated on a 4-point Likert scale (1-4). A sumscore has to be calculated for each subscale, ranging from 20 to 80 each, with higher scores indicating higher levels of anxiety.
Time frame: Difference from baseline (visit 2, day -2) of depressive symptoms to end of treatment (visit 5, day 14)
Patient reported outcomes (PRO)
The patient reported outcomes will be assessed at separate time points before and after Cannabidiol administration using a set of items assessing effects of the treatment as well as treatment burden on a five-point Likert scale (0 to 4) with higher values indicating more positive effects.
Time frame: On visit 3 (day 1 of treatment), visit 4 (day 7 of treatment), visit 5 (day 14, end of treatment) and during follow up visits 6 (day 28), 7 (day 42), 8 (day 105), 9 (day 196)
CBD plasma levels
The CBD plasma levels will be determined at separate time points before and after Cannabidiol administration to detect effects of active intervention on blood plasma levels. (Only participants enrolled at CIMH study site).
Time frame: On visit 3 (day 1 of treatment) and visit 5 (day 14, end of treatment)
Adverse Events (AEs) and Serious Adverse Events (SAEs)
Rate of adverse events and serious adverse events.
Time frame: On visit 3 (day 1 of treatment), visit 4 (day 7 of treatment), visit 5 (day 14, end of treatment) and during follow up visits 6 (day 28), 7 (day 42), 8 (day 105), 9 (day 196)
Time to relapse
Time from baseline (visit 2, day -2) to relapse to alcohol use (i.e. any alcohol use) (in days), assessed using the Form-90 semi-structured interview (Timeline Follow Back).
Time frame: On visit 5 (day 14, end of treatment) and during follow up visits 6 (day 28), 7 (day 42), 8 (day 105), 9 (day 196)
Cumulative alcohol consumption during the follow-up period
Cumulative alcohol consumption (in grams alcohol) during the follow-up period of 182 days (+/- 7 days), assessed using the Form-90 semi-structured interview (Timeline Follow Back).
Time frame: On visit 5 (day 14, end of treatment) and during follow up visits 6 (day 28), 7 (day 42), 8 (day 105), 9 (day 196)
Percent heavy drinking days during the follow-up period
Percent heavy drinking days during the follow-up period of 182 days (+/- 7 days), assessed using the Form-90 semi-structured interview (Timeline Follow Back).
Time frame: On visit 5 (day 14, end of treatment) and during follow up visits 6 (day 28), 7 (day 42), 8 (day 105), 9 (day 196)
Average weekly alcohol consumption during the follow-up period
Average weekly alcohol consumption assessed via smartphone-based e-diary every 7 days during the follow-up period of 182 days (+/- 7 days) (optional, only for patients that agree to use the study-specific app).
Time frame: Every 7 days during the follow-up period of 182 days (+/- 7 days), starting after visit 5, i.e., end of treatment (day 14) and continuing until visit 9, i.e., end of follow up (day 196)
Maximum weekly craving during the follow-up period
Maximum weekly craving assessed via smartphone-based e-diary every 7 days during the follow-up period of 182 days (+/- 7 days) (optional, only for patients that agree to use the study-specific app).
Time frame: Every 7 days during the follow-up period of 182 days (+/- 7 days), starting after visit 5, i.e., end of treatment (day 14) and continuing until visit 9, i.e., end of follow up (day 196)
Neural Brain Activation during functional magnetic resonance imaging
Differences from baseline of neural brain activation to visit 5, measured using the blood oxygenated level dependent (BOLD) response, during presentation of alcohol cues, during the presentation of natural reward cues, during inhibition of motor responses, during presentation of emotional faces and neutral shapes and functional connectivity during resting state (only for patients enrolled at CIMH study site).
Time frame: Differences from baseline (visit 2, day -2) to visit 5 (day 14, end of treatment)
Alcohol Craving during functional magnetic resonance imaging
Differences from baseline of alcohol craving (visual analogue scale) during the functional magnetic resonance imaging (fMRI) to visit 5 (only for patients enrolled at CIMH study site).
Time frame: Differences from baseline (visit 2, day -2) to visit 5 (day 14, end of treatment)
Response Times during functional magnetic resonance imaging
Differences in response times (i.e., time taken to respond) during functional magnetic resonance imaging (fMRI) from baseline to visit 5 (only for patients enrolled at CIMH study site).
Time frame: Differences from baseline (visit 2, day -2) to visit 5 (day 14, end of treatment)
Rates of Errors during functional magnetic resonance imaging
Differences in rates of errors during functional magnetic resonance imaging (fMRI) from baseline to visit 5 (only for patients enrolled at CIMH study site)
Time frame: Differences from baseline (visit 2, day -2) to visit 5 (day 14, end of treatment)
Rates of Correct Responses during functional magnetic resonance imaging
Differences in rates of correct responses during functional magnetic resonance imaging (fMRI) from baseline to visit 5 (only for patients enrolled at CIMH study site)
Time frame: Differences from baseline (visit 2, day -2) to visit 5 (day 14, end of treatment)
Omission Rates during functional magnetic resonance imaging
Differences in omission rates (i.e., rate of failure to respond when a response is expected) during functional magnetic resonance imaging (fMRI) from baseline to visit 5 (only for patients enrolled at CIMH study site)
Time frame: Differences from baseline (visit 2, day -2) to visit 5 (day 14, end of treatment)
Plan to share: Yes — Individual de-identified data will be shared, specifically individual participant data that underlie the results of the trial (i.e. primary outcome data [OCDS-G scores]) will be made available with a respective data dictionary. Secondary Outcome data (e.g. fMRI data) will be made available on aggregated group level (e.g. for the purpose of meta-analyses). Related documents, specifically the study protocol, statistical analysis plan and analytic code will be shared in open-access online repositories. Aggregated data will be made available to publicly accessible repositories (Neurosynth.org), e.g. for the purpose of meta-analyses.
Supporting information: Study protocol, Statistical analysis plan
Time frame: Data will be available upon publication of the results until 3 years after that.
Access criteria: Individual data will be shared with researchers who provide a methodologically sound proposal (sent to the Principal Investigator/Study Chair of the Trial).
Started Jul 2025 (actual). Primary completion is estimated for Apr 2028, 32 months after the start.
Of 122 non-industry phase 2 interventional studies under Alcoholism, half reached primary completion within 35 months of starting (the median), counting those still running; a quarter within 23 and three quarters within 59. This study's planned 32 months is close to that.
Counting every sponsor, half of 134 studies reached it within 33 months; a quarter within 21 and three quarters within 59.
How these figures are worked out, and which studies are left out of them.
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Studies of the drug tested here: Cannabidiol
Central Institute of Mental Health, Mannheim