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Completed

NCT Number: NCT04627922

N-Acetylcysteine for Smoking Cessation in Tobacco and Cannabis Co-Use

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.

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Key information

Conditions

Cannabis Use Chemically-Induced Disorders Drug Use Disorder Marijuana Abuse Mental Disorders Substance-Related Disorders Tobacco Use Disorder

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 4

Primary location

San Francisco Veterans Affairs Medical Center

San Francisco, California, 94121, United States

About this study

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.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

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 TLFB, and have positive urine THC at Week 0 or up to 30 days prior; 3) meet criteria for TUD in the past 12 months per 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).

Exclusion criteria

  • 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.

Treatment and study plan

N-acetyl cysteine

Drug

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.

Other names: NAC

Placebo Comparator

Other

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)

Behavioral

Participants in both groups will receive 8 weekly cognitive behavioral therapy sessions for substance use disorder targeting both tobacco and cannabis use.

Other names: CBT

Primary outcomes

  1. Change in the mean days of cannabis use over time

    Time frame: Up to Week 12

    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 of use over time will be reported by group.

  2. Change in the mean number of cigarettes used over time

    Time frame: Up to Week 12

    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 over time will be reported by group.

  3. Change in the mean number of days of cigarette use over time

    Time frame: Up to Week 12

    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 of cigarette use by group over time will be reported.

  4. 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.

  5. 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.

  6. Change in Scores on the Fagerstrom Test for Nicotine Dependence (FTND) over time

    Time frame: Up to 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.

  7. Change in Scores on the Questionnaire on Smoking Urges (QSU-Brief): Desire to smoke over time

    Time frame: Up to 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) and scores are calculated by summing the item scores. The change in the average score by group will be reported.

  8. Change in Scores on the Questionnaire on Smoking Urges (QSU-Brief): Nicotine withdrawal over time

    Time frame: Up to 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) and scores are calculated by summing the item scores. The change in the average score by group will be reported.

  9. Change in Scores on the Questionnaire on Smoking Urges (QSU-Brief): Total over time

    Time frame: Up to 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) and total scores are calculated by summing the item scores. The change in the average score by group will be reported.

  10. Change in Scores on the Cannabis Use Disorder Identification Test - Revised (CUDIT-R) over time

    Time frame: Up to 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. Scores of 8 or more indicate hazardous cannabis use, while scores of 12 or more indicate a possible cannabis use disorder for which further intervention may be required. The change in the average score by group will be reported.

  11. Change in Scores on the Marijuana Craving Questionnaire Short Form (MCQ-SF) Total over time

    Time frame: Up to 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) and scores are using the mean to the corresponding item. Total Scores are the sum of the means for the 4 subscales. The change in the average score by group will be reported.

Sponsors and collaborators

Lead sponsor

Ellen Herbst

Other

Collaborators

  • Tobacco Related Disease Research Program

Registry information

Official study title

N-Acetylcysteine for Smoking Cessation in Tobacco and Cannabis Co-Use: A Randomized Controlled Trial

Acronym: NAC_CUD-TUD

Important dates

Study start
2021
Primary completion
2025
Study completion
2025
First posted
Nov 13, 2020
Registry last updated
Mar 20, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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