Cannabis UsePhase 4NAC_CUD-TUDNCT04627922
N-Acetylcysteine for Smoking Cessation in Tobacco and Cannabis Co-Use
A Phase 4 study testing N-Acetyl cysteine and Cognitive behavioral therapy (CBT) in people with Cannabis Use and Tobacco Use Disorder, run by Ellen Herbst at 1 site in United States.
Trial summary
Tobacco and cannabis co-use is a common and growing public health problem, especially in states that have legalized cannabis. There are no pharmacologic treatments for co-occurring tobacco and cannabis use. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Cannabis Use, Tobacco Use Disorder, Drug Use Disorder
- What is being tested?
- N-Acetyl cysteine and Cognitive behavioral therapy (CBT)
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 41 participants
- Where
- 1 siteUnited States
- Study dates
- 25 Aug 2021to 30 Jun 2025
- Phase
- Phase 4
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Participants will be male and female smokers ages 18 and over who: 1) have smoked 2 cigarettes per day in 15 of the past 30 days, or an average of 1 cigarettes per day for the past 30 days; 2) endorse the use of cannabis within the past 30 days, reported by Timeline Follow-Back (TLFB), and have positive urine tetrahydrocannabinol (THC) at Week 0 or up to 30 days prior; 3) meet criteria for tobacco use disorder (TUD) in the past 12 months per Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), assessed by medical record review and clinical assessment; and 4) consent to receive interventions to stop smoking cigarettes and reducing cannabis use. Although co-users can use tobacco and cannabis simultaneously (i.e. in "spliffs") and other forms of nicotine and tobacco, participants must smoke combustible cigarettes that are not mixed with cannabis on a daily basis to participate. Individuals of childbearing potential (ages 18-55) must have a negative urine pregnancy test at the time of screening. Individuals who have been prescribed bupropion for depression, not smoking cessation, are eligible to participate in this study. All participants must be California residents (Veterans enrolled in VA healthcare in another state are eligible).
Who cannot join
- 1) Psychotic disorders, bipolar disorder, neurocognitive disorder, or other psychiatric or medical conditions judged by the PI to be unstable in the past 30 days, based on screening results and/or medical record review. 2) Concurrent participation in another pharmacological tobacco cessation study. 3) Individuals who are pregnant or lactating. 4) Non-study NAC use at enrollment or at any time during the study period. 5) Use of medications for TUD (NRT, bupropion, or varenicline) at enrollment or at any time during the study period. 6) A suicide attempt or suicidal ideation with intent in the 30 days prior to enrollment. 7) Non-residents of California or Veterans in another state who are not enrolled in VA healthcare.
Trial locations and contacts
1 site in 1 country.
United States1 site
San Francisco Veterans Affairs Medical Center
San Francisco, California, 94121
About this study
Official title: N-Acetylcysteine for Smoking Cessation in Tobacco and Cannabis Co-Use: A Randomized Controlled Trial
Tobacco and cannabis co-use is a common and growing public health problem, especially in states that have legalized cannabis. There are no pharmacologic treatments for co-occurring tobacco and cannabis use. Co-use may make quitting either substance more difficult, given the synergistic effects of cannabis and nicotine on neurobiological systems that mediate reward and shared cues reinforcing co-use. N-acetylcysteine (NAC), an FDA-approved medication and over-the-counter supplement, has shown promise in animal studies and randomized controlled trials (RCTs) in reducing tobacco and cannabis craving and use.
Read the detailed description
N-acetylcysteine (NAC), an FDA-approved medication and over-the-counter supplement, has shown promise in animal studies and randomized controlled trials (RCTs) in reducing tobacco and cannabis craving and use. NAC's efficacy in treating addiction may be attributable to its central nervous system effects in reducing excessive glutamatergic activity, oxidative stress, and inflammation. NAC has been shown to improve cognition and reduce impulsivity, which in turn may strengthen inhibitory control when presented with contextual cues. To date, no RCT has examined NAC for smoking cessation in the setting of tobacco-cannabis co-use. In a double-blind, placebo-controlled RCT, the investigators will examine a novel pharmacological treatment, NAC, for concurrent tobacco use disorder (TUD) and cannabis use in dual users of tobacco and cannabis. Sixty adult regular cigarette smokers who 1) have smoked 2 cigarettes per day in 15 of the past 30 days, or an average of 1 cigarettes per day for the past 30 days and 2) use cannabis regularly and 3) consent to receive interventions to stop smoking cigarettes and using cannabis will be randomized to receive NAC 3600 mg per day or placebo over 8 weeks. Participants in both groups will receive 8 weekly cognitive behavioral therapy sessions addressing both tobacco and cannabis use. Outcomes will be assessed at Weeks 0, 4, 8, and 12. Primary aims are to determine NAC's efficacy in decreasing cigarette use, nicotine dependence levels, and craving; and cannabis use, and craving. Exploratory aims include examination of changes in neurocognition with NAC and their potential mediational effects on cigarette and cannabis use outcomes.
NAC SUB-STUDY:
Because of the significant clinical and economic burden imposed by tobacco and cannabis use, it is important to understand the mechanism underlying the progression of tobacco (TUD) and cannabis use disorders (CUD) and any potential treatments. TUD and CUD are associated with elevated oxidative stress and chronic inflammation. It has been suggested that patients dependent on these substances have dysregulated markers of oxidation and inflammation, including gluthathione, erythrocyte sedimentation rate (ESR), C-Reactive protein (CRP), Interleukin-6 (IL-6).
In this sub-study, baseline levels of commonly utilized serum markers of oxidation status and inflammation will be measured in 20 adults recruited under the main study, with the option of being a part of the sub-study who also demonstrate concurrent TUD and cannabis use. The correlation will be determined between changes in serum markers of oxidative stress and magnitude of use of cigarettes and cannabis. If successful, the investigator will establish regulatory patterns of oxidative stress and inflammation in TUD and with concurrent cannabis use for the first time and will implicate oxidative stress and inflammation as playing key roles in the progression and severity of co-occurring TUD and CUD.
- Conditions
- Cannabis Use, Tobacco Use Disorder, Drug Use Disorder
- Being tested
- N-Acetyl cysteine, Placebo comparator, Cognitive behavioral therapy (CBT)
- Keywords
- Tobacco, Cannabis, N-acetylcysteine, NAC
- Medical subject headings
- Tobacco Use Disorder, Substance-Related Disorders, Marijuana Abuse
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
N-Acetyl cysteineDrug
Also called NAC
The investigators will examine N-acetyl cysteine to treat concurrent tobacco use disorder and cannabis use in a double-blind, placebo-controlled RCT. Eligible regular cigarette smokers with current tobacco use disorder and cannabis use will be randomized to receive NAC 3600 mg per day over 8 weeks.
Placebo comparatorOther
The investigators will examine N-acetyl cysteine to treat concurrent tobacco use disorder and cannabis use in a double-blind, placebo-controlled RCT. Eligible regular cigarette smokers with current tobacco use disorder and cannabis use will be randomized to receive placebo per day over 8 weeks.
Cognitive behavioral therapy (CBT)Behavioural
Also called CBT
Participants in both groups will receive 8 weekly cognitive behavioral therapy sessions for substance use disorder targeting both tobacco and cannabis use.
| Study group | Role | What they receive |
|---|---|---|
| N-acetyl cysteine (NAC) & cognitive behavioral therapy | Experimental | N-acetyl cysteine (NAC) \& cognitive behavioral therapy experimental arm consists of 30 regular cigarette smokers and cannabis users with current TUD, who will be randomized to receive N-acetyl cysteine 3600 mg per day over 8 weeks to experimental arm. Participants will also receive weekly cognitive behavioral therapy for substance use disorders targeting TUD and cannabis use. Receives: Drug: N-Acetyl cysteine; Behavioral: Cognitive behavioral therapy (CBT) |
| Placebo Comparator: Placebo & cognitive behavioral therapy | Placebo comparator | Placebo comparator \& cognitive behavioral therapy arm consists of 30 regular cigarette smokers and cannabis users with current TUD, who will be randomized to receive placebo over 8 weeks. Participants will also receive weekly cognitive behavioral therapy for substance use disorders targeting TUD and cannabis use. Receives: Other: Placebo comparator; Behavioral: Cognitive behavioral therapy (CBT) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in the Mean Days of Cannabis Use Over Time
Days of cannabis use will be determined by weekly self-report use of cannabis assessed with Timeline Follow-back (TLFB) which uses a calendar with specific anchor dates to identify the number of 'use days'. The change in the mean number of days reported at baseline and at the week 12 visit will be reported by group.
Measured: Baseline and 12 weeks
Change in the Mean Number of Cigarettes Used Over Time
Weekly self-report use of cigarettes will be assessed with Timeline Follow-back (TLFB) which uses a calendar with specific anchor dates to identify the quantity of use. The change in the mean number of cigarettes used reported at baseline and at the week 12 visit will be reported by group.
Measured: Baseline and 12 weeks
Change in the Mean Number of Days of Cigarette Use Over Time
Weekly self-report use of cigarettes will be assessed with Timeline Follow-back (TLFB) which uses a calendar with specific anchor dates to identify the frequency of use. The change in the mean number of days reported at baseline and at the week 12 visit will be reported by group.
Measured: Baseline and 12 weeks
Percentage of Participants With Biochemically Verified, Point-prevalent Abstinence at Week 8
Biochemically verified abstinence is defined as a participant self-report of not smoking and a saliva sample to detect the presence or absence of salivary cotinine. Salivary cotinine tests are an established method to biochemically verify a participant's reported smoking status.
Measured: At Week 8
Percentage of Participants With Biochemically Verified Point Prevalent Abstinence at Week 12
Biochemically verified abstinence is defined as a participant self-report of not smoking and a saliva sample to detect the presence or absence of salivary cotinine. Salivary cotinine tests are an established method to biochemically verify a participant's reported smoking status.
Measured: At Week 12
Change in Scores on the Fagerstrom Test for Nicotine Dependence (FTND) Over Time
The Fagerström Test for Nicotine Dependence is a standard instrument for assessing the intensity of physical addiction to nicotine. It contains six items that evaluate the quantity of cigarette consumption, the compulsion to use, and dependence. In scoring the Fagerstrom Test for Nicotine Dependence, yes/no items are scored from 0 to 1 and multiple-choice items are scored from 0 to 3. The items are summed to yield a total score of 0-10. The higher the total Fagerström score, the more intense is the patient's physical dependence on nicotine. The change in the average score by group will be reported.
Measured: Baseline and 12 weeks
Change in Scores on the Questionnaire on Smoking Urges (QSU-Brief): Total Over Time
The QSU-Brief consists of 10 statements about the respondent's feelings and thoughts about his or her desire to smoke cigarettes as he or she is completing the questionnaire (i.e., right now). Each response is scored a number ranging from 1 (strongly disagree) to 7 (strongly agree). The items are summed to yield a total score of 10-70. Higher total scores indicate stronger current smoking urges. The change in the average total score between baseline and week 12 will be reported by group.
Measured: Baseline and 12 weeks
Change in Scores on the Cannabis Use Disorder Identification Test - Revised (CUDIT-R) Over Time
This questionnaire was designed for self-administration and is scored by adding each of the 8 items relating to cannabis use over the past six months. Question 1-7 are scored on a 0-4 scale Question 8 is scored 0,2, or 4. Total score is calculated by summing the items for a total score of 0-32. Total scores of 8 or more indicate hazardous cannabis use, while total scores of 12 or more indicate a possible cannabis use disorder for which further intervention may be required. The change in the average total score between baseline and week 12 will be reported by group.
Measured: Baseline and 12 weeks
Change in Total Scores on the Marijuana Craving Questionnaire Short Form (MCQ-SF) Total Over Time
This 12-item multidimensional measure assesses cannabis craving based on 4 factors: Compulsivity, Emotionality, Expectancy, Purposefulness. Each item asks about the respondent's feelings and thoughts about smoking marijuana as he or she is completing the questionnaire (i.e., right now). Each response is scored a number ranging from 1 (strongly disagree) to 7 (strongly agree). Each of the 4 factors (subscales) consist of 3 items which are scored by taking the total of the responses in that scale for a total possible subscale score of 3-21. The total score is calculated by summing the total scores for the 4 subscales for a total score range of 12-84 The change in the average total score from baseline to week 12 will be reported by group.
Measured: Baseline and 12 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted13 Nov 2020
- Study start25 Aug 2021
- Primary completion30 Jun 2025
- Study completion30 Jun 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Publications (4)Papers the sponsor has linked to this study.
- Other trials for Cannabis UseStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 4
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind
- Who is masked
- Participant, Investigator
- Enrolment
- 41 participants (actual)
Sponsor and investigators
- Lead sponsor
- Ellen Herbst
- Sponsor type
- University, hospital or other
- Collaborators
- Tobacco Related Disease Research Program
- Responsible party
- Sponsor-investigator, Ellen Herbst, University of California, San Francisco
- Investigators
- Ellen Herbst, MD, Principal investigator, San Francisco Veterans Affairs Medical CenterMadeline Martinez Rivas, PhD, Study director, San Francisco Veterans Affairs Medical Center
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04627922
- Sponsor's protocol ID
- 20-31475
- Acronym
- NAC_CUD-TUD
- Status last verified
- Aug 2026
- First submitted
- 3 Nov 2020
- Last updated
- 11 Aug 2026
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Schauer GL, Berg CJ, Kegler MC, Donovan DM, Windle M. Assessing the overlap between tobacco and marijuana: Trends in patterns of co-use of tobacco and marijuana in adults from 2003-2012. Addict Behav. 2015 Oct;49:26-32. doi: 10.1016/j.addbeh.2015.05.012. Epub 2015 May 23.
PubMed 26036666Davis CN, Slutske WS, Martin NG, Agrawal A, Lynskey MT. Identifying subtypes of cannabis users based on simultaneous polysubstance use. Drug Alcohol Depend. 2019 Dec 1;205:107696. doi: 10.1016/j.drugalcdep.2019.107696. Epub 2019 Oct 28.
PubMed 31726429Eisenlohr-Moul TA, Peters JR, Pond RS Jr, DeWall CN. Both trait and state mindfulness predict lower aggressiveness via anger rumination: A multilevel mediation analysis. Mindfulness (N Y). 2016 Jun;7(3):713-726. doi: 10.1007/s12671-016-0508-x. Epub 2016 Mar 9.
PubMed 27429667Herbst ED, Pennington DL, Borsari B, Manuel J, Yalch M, Alcid E, Martinez Rivas M, Delacruz J, Rossi N, Garcia B, Wong N, Batki SL. N-acetylcysteine for smoking cessation among dual users of tobacco and cannabis: Protocol and rationale for a randomized controlled trial. Contemp Clin Trials. 2023 Aug;131:107250. doi: 10.1016/j.cct.2023.107250. Epub 2023 Jun 2.
PubMed 37271412
Study at a glance
From the registry record, last updated by the sponsor on 11 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- N-Acetylcysteine for Smoking Cessation in Tobacco and Cannabis Co-Use: A Randomized Controlled Trial
- ClinicalTrials.gov ID
- NCT04627922
- Acronym / sponsor ID
- NAC_CUD-TUD / 20-31475
- Conditions
- Cannabis Use, Tobacco Use Disorder, Drug Use Disorder
- Keywords
- Tobacco, Cannabis, N-acetylcysteine, NAC
- Phase
- Phase 4
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 41 participants (actual)
- Lead sponsor
- Ellen HerbstUniversity, hospital or other
- Collaborators
- Tobacco Related Disease Research Program
- Study start
- 25 Aug 2021 (actual)
- Primary completion
- 30 Jun 2025 (actual)
- Study completion
- 30 Jun 2025 (actual)
- First posted
- 13 Nov 2020 (actual)
- Results
- Posted 11 Aug 2026
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Tobacco and cannabis co-use is a common and growing public health problem, especially in states that have legalized cannabis. There are no pharmacologic treatments for co-occurring tobacco and cannabis use. Co-use may make quitting either substance more difficult, given the synergistic effects of cannabis and nicotine on neurobiological systems that mediate reward and shared cues reinforcing co-use. N-acetylcysteine (NAC), an FDA-approved medication and over-the-counter supplement, has shown promise in animal studies and randomized controlled trials (RCTs) in reducing tobacco and cannabis craving and use.
Detailed description
N-acetylcysteine (NAC), an FDA-approved medication and over-the-counter supplement, has shown promise in animal studies and randomized controlled trials (RCTs) in reducing tobacco and cannabis craving and use. NAC's efficacy in treating addiction may be attributable to its central nervous system effects in reducing excessive glutamatergic activity, oxidative stress, and inflammation. NAC has been shown to improve cognition and reduce impulsivity, which in turn may strengthen inhibitory control when presented with contextual cues. To date, no RCT has examined NAC for smoking cessation in the setting of tobacco-cannabis co-use. In a double-blind, placebo-controlled RCT, the investigators will examine a novel pharmacological treatment, NAC, for concurrent tobacco use disorder (TUD) and cannabis use in dual users of tobacco and cannabis. Sixty adult regular cigarette smokers who 1) have smoked 2 cigarettes per day in 15 of the past 30 days, or an average of 1 cigarettes per day for the past 30 days and 2) use cannabis regularly and 3) consent to receive interventions to stop smoking cigarettes and using cannabis will be randomized to receive NAC 3600 mg per day or placebo over 8 weeks. Participants in both groups will receive 8 weekly cognitive behavioral therapy sessions addressing both tobacco and cannabis use. Outcomes will be assessed at Weeks 0, 4, 8, and 12. Primary aims are to determine NAC's efficacy in decreasing cigarette use, nicotine dependence levels, and craving; and cannabis use, and craving. Exploratory aims include examination of changes in neurocognition with NAC and their potential mediational effects on cigarette and cannabis use outcomes.
NAC SUB-STUDY:
Because of the significant clinical and economic burden imposed by tobacco and cannabis use, it is important to understand the mechanism underlying the progression of tobacco (TUD) and cannabis use disorders (CUD) and any potential treatments. TUD and CUD are associated with elevated oxidative stress and chronic inflammation. It has been suggested that patients dependent on these substances have dysregulated markers of oxidation and inflammation, including gluthathione, erythrocyte sedimentation rate (ESR), C-Reactive protein (CRP), Interleukin-6 (IL-6).
In this sub-study, baseline levels of commonly utilized serum markers of oxidation status and inflammation will be measured in 20 adults recruited under the main study, with the option of being a part of the sub-study who also demonstrate concurrent TUD and cannabis use. The correlation will be determined between changes in serum markers of oxidative stress and magnitude of use of cigarettes and cannabis. If successful, the investigator will establish regulatory patterns of oxidative stress and inflammation in TUD and with concurrent cannabis use for the first time and will implicate oxidative stress and inflammation as playing key roles in the progression and severity of co-occurring TUD and CUD.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind (participant, investigator)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| N-acetyl cysteine (NAC) & cognitive behavioral therapy | Experimental | Drug: N-Acetyl cysteine, Behavioral: Cognitive behavioral therapy (CBT)N-acetyl cysteine (NAC) \& cognitive behavioral therapy experimental arm consists of 30 regular cigarette smokers and cannabis users with current TUD, who will be randomized to receive N-acetyl cysteine 3600 mg per day over 8 weeks to experimental arm. Participants will also receive weekly cognitive behavioral therapy for substance use disorders targeting TUD and cannabis use. |
| Placebo Comparator: Placebo & cognitive behavioral therapy | Placebo comparator | Other: Placebo comparator, Behavioral: Cognitive behavioral therapy (CBT)Placebo comparator \& cognitive behavioral therapy arm consists of 30 regular cigarette smokers and cannabis users with current TUD, who will be randomized to receive placebo over 8 weeks. Participants will also receive weekly cognitive behavioral therapy for substance use disorders targeting TUD and cannabis use. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (1 listed)
- Participants will be male and female smokers ages 18 and over who: 1) have smoked 2 cigarettes per day in 15 of the past 30 days, or an average of 1 cigarettes per day for the past 30 days; 2) endorse the use of cannabis within the past 30 days, reported by Timeline Follow-Back (TLFB), and have positive urine tetrahydrocannabinol (THC) at Week 0 or up to 30 days prior; 3) meet criteria for tobacco use disorder (TUD) in the past 12 months per Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), assessed by medical record review and clinical assessment; and 4) consent to receive interventions to stop smoking cigarettes and reducing cannabis use. Although co-users can use tobacco and cannabis simultaneously (i.e. in "spliffs") and other forms of nicotine and tobacco, participants must smoke combustible cigarettes that are not mixed with cannabis on a daily basis to participate. Individuals of childbearing potential (ages 18-55) must have a negative urine pregnancy test at the time of screening. Individuals who have been prescribed bupropion for depression, not smoking cessation, are eligible to participate in this study. All participants must be California residents (Veterans enrolled in VA healthcare in another state are eligible).
Key exclusion criteria (1 listed)
- 1) Psychotic disorders, bipolar disorder, neurocognitive disorder, or other psychiatric or medical conditions judged by the PI to be unstable in the past 30 days, based on screening results and/or medical record review. 2) Concurrent participation in another pharmacological tobacco cessation study. 3) Individuals who are pregnant or lactating. 4) Non-study NAC use at enrollment or at any time during the study period. 5) Use of medications for TUD (NRT, bupropion, or varenicline) at enrollment or at any time during the study period. 6) A suicide attempt or suicidal ideation with intent in the 30 days prior to enrollment. 7) Non-residents of California or Veterans in another state who are not enrolled in VA healthcare.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| N-Acetyl cysteineAlso: NACThe investigators will examine N-acetyl cysteine to treat concurrent tobacco use disorder and cannabis use in a double-blind, placebo-controlled RCT. Eligible regular cigarette smokers with current tobacco use disorder and cannabis use will be randomized to receive NAC 3600 mg per day over 8 weeks. | Drug | N-acetyl cysteine (NAC) & cognitive behavioral therapy |
| Placebo comparatorThe investigators will examine N-acetyl cysteine to treat concurrent tobacco use disorder and cannabis use in a double-blind, placebo-controlled RCT. Eligible regular cigarette smokers with current tobacco use disorder and cannabis use will be randomized to receive placebo per day over 8 weeks. | Other | Placebo Comparator: Placebo & cognitive behavioral therapy |
| Cognitive behavioral therapy (CBT)Also: CBTParticipants in both groups will receive 8 weekly cognitive behavioral therapy sessions for substance use disorder targeting both tobacco and cannabis use. | Behavioural | N-acetyl cysteine (NAC) & cognitive behavioral therapy, Placebo Comparator: Placebo & cognitive behavioral therapy |
Primary outcome
Change in the Mean Days of Cannabis Use Over Time
Time frame: Baseline and 12 weeks
Days of cannabis use will be determined by weekly self-report use of cannabis assessed with Timeline Follow-back (TLFB) which uses a calendar with specific anchor dates to identify the number of 'use days'. The change in the mean number of days reported at baseline and at the week 12 visit will be reported by group.
Change in the Mean Number of Cigarettes Used Over Time
Time frame: Baseline and 12 weeks
Weekly self-report use of cigarettes will be assessed with Timeline Follow-back (TLFB) which uses a calendar with specific anchor dates to identify the quantity of use. The change in the mean number of cigarettes used reported at baseline and at the week 12 visit will be reported by group.
Change in the Mean Number of Days of Cigarette Use Over Time
Time frame: Baseline and 12 weeks
Weekly self-report use of cigarettes will be assessed with Timeline Follow-back (TLFB) which uses a calendar with specific anchor dates to identify the frequency of use. The change in the mean number of days reported at baseline and at the week 12 visit will be reported by group.
Percentage of Participants With Biochemically Verified, Point-prevalent Abstinence at Week 8
Time frame: At Week 8
Biochemically verified abstinence is defined as a participant self-report of not smoking and a saliva sample to detect the presence or absence of salivary cotinine. Salivary cotinine tests are an established method to biochemically verify a participant's reported smoking status.
Percentage of Participants With Biochemically Verified Point Prevalent Abstinence at Week 12
Time frame: At Week 12
Biochemically verified abstinence is defined as a participant self-report of not smoking and a saliva sample to detect the presence or absence of salivary cotinine. Salivary cotinine tests are an established method to biochemically verify a participant's reported smoking status.
Change in Scores on the Fagerstrom Test for Nicotine Dependence (FTND) Over Time
Time frame: Baseline and 12 weeks
The Fagerström Test for Nicotine Dependence is a standard instrument for assessing the intensity of physical addiction to nicotine. It contains six items that evaluate the quantity of cigarette consumption, the compulsion to use, and dependence. In scoring the Fagerstrom Test for Nicotine Dependence, yes/no items are scored from 0 to 1 and multiple-choice items are scored from 0 to 3. The items are summed to yield a total score of 0-10. The higher the total Fagerström score, the more intense is the patient's physical dependence on nicotine. The change in the average score by group will be reported.
Change in Scores on the Questionnaire on Smoking Urges (QSU-Brief): Total Over Time
Time frame: Baseline and 12 weeks
The QSU-Brief consists of 10 statements about the respondent's feelings and thoughts about his or her desire to smoke cigarettes as he or she is completing the questionnaire (i.e., right now). Each response is scored a number ranging from 1 (strongly disagree) to 7 (strongly agree). The items are summed to yield a total score of 10-70. Higher total scores indicate stronger current smoking urges. The change in the average total score between baseline and week 12 will be reported by group.
Change in Scores on the Cannabis Use Disorder Identification Test - Revised (CUDIT-R) Over Time
Time frame: Baseline and 12 weeks
This questionnaire was designed for self-administration and is scored by adding each of the 8 items relating to cannabis use over the past six months. Question 1-7 are scored on a 0-4 scale Question 8 is scored 0,2, or 4. Total score is calculated by summing the items for a total score of 0-32. Total scores of 8 or more indicate hazardous cannabis use, while total scores of 12 or more indicate a possible cannabis use disorder for which further intervention may be required. The change in the average total score between baseline and week 12 will be reported by group.
Change in Total Scores on the Marijuana Craving Questionnaire Short Form (MCQ-SF) Total Over Time
Time frame: Baseline and 12 weeks
This 12-item multidimensional measure assesses cannabis craving based on 4 factors: Compulsivity, Emotionality, Expectancy, Purposefulness. Each item asks about the respondent's feelings and thoughts about smoking marijuana as he or she is completing the questionnaire (i.e., right now). Each response is scored a number ranging from 1 (strongly disagree) to 7 (strongly agree). Each of the 4 factors (subscales) consist of 3 items which are scored by taking the total of the responses in that scale for a total possible subscale score of 3-21. The total score is calculated by summing the total scores for the 4 subscales for a total score range of 12-84 The change in the average total score from baseline to week 12 will be reported by group.
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 11 Aug 2026.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- Background: PubMed 26036666Schauer GL, Berg CJ, Kegler MC, Donovan DM, Windle M. Assessing the overlap between tobacco and marijuana: Trends in patterns of co-use of tobacco and marijuana in adults from 2003-2012. Addict Behav. 2015 Oct;49:26-32. doi: 10.1016/j.addbeh.2015.05.012. Epub 2015 May 23.
- Background: PubMed 31726429Davis CN, Slutske WS, Martin NG, Agrawal A, Lynskey MT. Identifying subtypes of cannabis users based on simultaneous polysubstance use. Drug Alcohol Depend. 2019 Dec 1;205:107696. doi: 10.1016/j.drugalcdep.2019.107696. Epub 2019 Oct 28.
- Background: PubMed 27429667Eisenlohr-Moul TA, Peters JR, Pond RS Jr, DeWall CN. Both trait and state mindfulness predict lower aggressiveness via anger rumination: A multilevel mediation analysis. Mindfulness (N Y). 2016 Jun;7(3):713-726. doi: 10.1007/s12671-016-0508-x. Epub 2016 Mar 9.
- Derived from this study: PubMed 37271412Herbst ED, Pennington DL, Borsari B, Manuel J, Yalch M, Alcid E, Martinez Rivas M, Delacruz J, Rossi N, Garcia B, Wong N, Batki SL. N-acetylcysteine for smoking cessation among dual users of tobacco and cannabis: Protocol and rationale for a randomized controlled trial. Contemp Clin Trials. 2023 Aug;131:107250. doi: 10.1016/j.cct.2023.107250. Epub 2023 Jun 2.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Ellen Herbst, MD principal investigator
San Francisco Veterans Affairs Medical Center
Madeline Martinez Rivas, PhD study director
San Francisco Veterans Affairs Medical Center
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 4 study testing N-Acetyl cysteine and Cognitive behavioral therapy (CBT) in people with Cannabis Use and Tobacco Use Disorder, run by Ellen Herbst at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 1 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 11 Aug 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 4 studies take place after a treatment is approved, to learn more about its long-term benefits and risks in everyday use.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 11 Aug 2026). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in the Mean Days of Cannabis Use Over Time (time frame: Baseline and 12 weeks). The study lists 9 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT04627922, which also lists 4 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 11 Aug 2026.