Marijuana Use
Conditions
Keywords
Naltrexone, Smoked Marijuana
Brief summary
The purpose of this study is to determine if the subjective effects of marijuana will be decreased by low-doses (\< 25 mg) of naltrexone and increased by high-doses (\> 50 mg) of naltrexone.
Detailed description
Laboratory animal studies demonstrate that endogenous cannabinoids and opioids are closely inter-related. We have completed a series of studies in marijuana smokers showing that a clinically-utilized dose of naltrexone (50 mg) enhanced the reinforcing and subjective effects of orally-administered tetrahydrocannabinol (THC), while a low naltrexone dose (12 mg) blunted the effects of THC. A better understanding of the effects of a range of naltrexone doses in combination with smoked marijuana has important implications for the following reasons: (1) Alcohol- and opioid-dependent patients receive high doses of naltrexone (50-150 mg), which may increase the abuse liability of marijuana, (2) Low-dose naltrexone blunts THC's intoxicating effects, suggesting potential utility as a treatment medication for marijuana dependence. This study will determine if naltrexone (0, 12, 25, 50, 100 mg) administration 45 min prior to marijuana administration (0, 3.27% THC) alters marijuana's subjective, cognitive or physiological effects. Marijuana smokers will spend approximately 5h/day for a total of 10 days in the outpatient laboratory. Participants will visit the outpatient laboratory 2-3 times per week, with a minimum 48-hr interval between sessions to allow for naltrexone clearance. These data will provide important information regarding the clinical use of naltrexone.
Interventions
DRUGPlacebo + Inactive Marijuana (0% THC)
One capsule containing placebo was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before marijuana administration.
DRUGPlacebo + Active Marijuana (3.27% THC)
One capsule containing placebo was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before administration of a marijuana cigarette containing 3.27% THC (ca. 800 mg) provided by the National Institute on Drug Abuse.
DRUGNaltrexone 12 Mg+ Active Marijuana (3.27% THC)
One capsule containing 12mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before active marijuana administration.
DRUGNaltrexone 25 Mg + Active Marijuana (3.27% THC)
One capsule containing 12mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before active marijuana administration.
DRUGNaltrexone 50 Mg+ Active Marijuana (3.27% THC)
One capsule containing 25mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before marijuana administration.
DRUGNaltrexone 100 Mg+ Active Marijuana (3.27% THC)
One capsule containing 50mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before marijuana administration.
DRUGNaltrexone 12 Mg + Inactive Marijuana (0% THC)
One capsule containing 12mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before inactive marijuana administration.
DRUGNaltrexone 25 Mg + Inactive Marijuana (0% THC)
One capsule containing 25mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before inactive marijuana administration.
DRUGNaltrexone 50 Mg + Inactive Marijuana (0% THC)
One capsule containing 50mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before inactive marijuana administration.
DRUGNaltrexone 100 Mg + Inactive Marijuana (0% THC)
One capsule containing 100mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before inactive marijuana administration.
Sponsors
Research Foundation for Mental Hygiene, Inc.
National Institute on Drug Abuse (NIDA)
New York State Psychiatric Institute
Study design
Allocation
RANDOMIZED
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Investigator)
Masking description
double-blind, placebo-controlled
Eligibility
Sex/Gender
ALL
Age
21 Years to 45 Years
Healthy volunteers
Yes
Inclusion criteria
* Current marijuana use * Able to perform study procedures * 21-45 years of age * Women practicing an effective form of birth control
Exclusion criteria
* Current, repeated illicit drug use (other than marijuana) * Presence of significant medical illness (e.g., diabetes, cardiovascular disease, hypertension, examination, laboratory hepatitis, clinically significant laboratory abnormalities, tests, 12-lead ECG, Mantoux test LFTs \> 3x upper limit of normal) * History of heart disease * Request for drug treatment * Current parole or probation * Pregnancy or current lactation * Recent history of significant violent behavior * Previous adverse reaction to naltrexone * Major current Axis I psychopathology Psychiatric interview (e.g., major depressive disorder, bipolar disorder, suicide risk, schizophrenia) * Current use of any prescription or over-the-counter medication
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Baseline compared to 6 week timepoint | All subjective effects were measured using visual analog scales (VAS), a series of 100 mm long lines labeled 'not at all' at one end (0 mm) and 'extremely' at the other end (100 mm). Participants were instructed to rate their subjective experiences on the line according to how they felt at that particular moment. Subjective assessments included measures of perceived marijuana strength, marijuana high, good effects of marijuana, and how much marijuana was liked. Marijuana's effects were determined by comparing the active and inactive marijuana conditions when paired with the placebo naltrexone condition (one comparison). Naltrexone's intrinsic effects were assessed by comparing placebo and each active dose of naltrexone (12, 25, 50, and 100 mg) under the inactive marijuana condition (four comparisons). Finally, the active marijuana- placebo naltrexone condition was compared to the active marijuana-active naltrexone conditions (four comparisons) |
| Change in Mean Psychomotor Task Performance as a Function of Marijuana Strength and Naltrexone Dose | Baseline compared to 6 week timepoint | Change in Digit Symbol Substitution Test (DSST) scores. Increasing scores indicate improvement, on a scale of 0-90. The task batteries included total correct attempts on a 3-min DSST. |
| Change in Mean Heart Rate as a Function of Marijuana Strength and Naltrexone Dose. | Baseline compared to 6 week timepoint | Change in mean heart rate as a function of marijuana and naltrexone dose |
Participant flow
Recruitment details
A total of 15 males and 14 females completed this study, which used a within-subject design such that each participant received 10 different drug treatments/interventions in total.
Participants by arm
| Arm | Count |
|---|---|
| Overall Number of Baseline Participants Baseline measures are only reported for the 29 participants who completed the study. | 29 |
| Total | 29 |
Baseline characteristics
| Characteristic | Overall Number of Baseline Participants |
|---|---|
| Age, Categorical <=18 years | 0 Participants |
| Age, Categorical >=65 years | 0 Participants |
| Age, Categorical Between 18 and 65 years | 29 Participants |
| Age, Continuous | 28.0 Years STANDARD_DEVIATION 1 |
| Region of Enrollment United States | 29 Participants |
| Sex: Female, Male Female | 14 Participants |
| Sex: Female, Male Male | 15 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk | EG002 affected / at risk | EG003 affected / at risk | EG004 affected / at risk | EG005 affected / at risk | EG006 affected / at risk | EG007 affected / at risk | EG008 affected / at risk | EG009 affected / at risk |
|---|---|---|---|---|---|---|---|---|---|---|
| deaths Total, all-cause mortality | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 |
| other Total, other adverse events | 0 / 49 | 0 / 49 | 0 / 49 | 7 / 49 | 12 / 49 | 1 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 |
| serious Total, serious adverse events | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 | 0 / 49 |
Outcome results
Primary
Change in Mean Heart Rate as a Function of Marijuana Strength and Naltrexone Dose.
Change in mean heart rate as a function of marijuana and naltrexone dose
Time frame: Baseline compared to 6 week timepoint
Population: A total of 29 participants were included in the final analysis
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Placebo + Marijuana (0.0%THC) | Change in Mean Heart Rate as a Function of Marijuana Strength and Naltrexone Dose. | 68.5 Heart rate (beats/minute) | Standard Deviation 0.5 |
| Placebo + Marijuana (3.27% THC) | Change in Mean Heart Rate as a Function of Marijuana Strength and Naltrexone Dose. | 70.7 Heart rate (beats/minute) | Standard Deviation 0.6 |
| Naltrexone (12mg) + Marijuana (0.0%THC) | Change in Mean Heart Rate as a Function of Marijuana Strength and Naltrexone Dose. | 65.8 Heart rate (beats/minute) | Standard Deviation 0.5 |
| Naltrexone (12mg) + Marijuana (3.27%THC) | Change in Mean Heart Rate as a Function of Marijuana Strength and Naltrexone Dose. | 72.1 Heart rate (beats/minute) | Standard Deviation 0.4 |
| Naltrexone (25mg) + Marijuana (0.0%THC) | Change in Mean Heart Rate as a Function of Marijuana Strength and Naltrexone Dose. | 67.3 Heart rate (beats/minute) | Standard Deviation 0.4 |
| Naltrexone (25mg) + Marijuana (3.27%THC) | Change in Mean Heart Rate as a Function of Marijuana Strength and Naltrexone Dose. | 72.7 Heart rate (beats/minute) | Standard Deviation 0.7 |
| Naltrexone (50mg) + Marijuana (0.0%THC) | Change in Mean Heart Rate as a Function of Marijuana Strength and Naltrexone Dose. | 65.6 Heart rate (beats/minute) | Standard Deviation 0.3 |
| Naltrexone (50mg) + Marijuana (3.27%THC) | Change in Mean Heart Rate as a Function of Marijuana Strength and Naltrexone Dose. | 72.2 Heart rate (beats/minute) | Standard Deviation 0.6 |
| Naltrexone (100mg) + Marijuana (0.0%THC) | Change in Mean Heart Rate as a Function of Marijuana Strength and Naltrexone Dose. | 67.7 Heart rate (beats/minute) | Standard Deviation 0.4 |
| Naltrexone (100mg) + Marijuana (3.27%THC) | Change in Mean Heart Rate as a Function of Marijuana Strength and Naltrexone Dose. | 72.4 Heart rate (beats/minute) | Standard Deviation 0.4 |
Primary
Change in Mean Psychomotor Task Performance as a Function of Marijuana Strength and Naltrexone Dose
Change in Digit Symbol Substitution Test (DSST) scores. Increasing scores indicate improvement, on a scale of 0-90. The task batteries included total correct attempts on a 3-min DSST.
Time frame: Baseline compared to 6 week timepoint
Population: Data from 29 participants were included in this analysis
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Placebo + Marijuana (0.0%THC) | Change in Mean Psychomotor Task Performance as a Function of Marijuana Strength and Naltrexone Dose | 86.2 units on a scale | Standard Error 1.8 |
| Placebo + Marijuana (3.27% THC) | Change in Mean Psychomotor Task Performance as a Function of Marijuana Strength and Naltrexone Dose | 86.1 units on a scale | Standard Error 1.7 |
| Naltrexone (12mg) + Marijuana (0.0%THC) | Change in Mean Psychomotor Task Performance as a Function of Marijuana Strength and Naltrexone Dose | 86.7 units on a scale | Standard Error 1.7 |
| Naltrexone (12mg) + Marijuana (3.27%THC) | Change in Mean Psychomotor Task Performance as a Function of Marijuana Strength and Naltrexone Dose | 84.7 units on a scale | Standard Error 1.6 |
| Naltrexone (25mg) + Marijuana (0.0%THC) | Change in Mean Psychomotor Task Performance as a Function of Marijuana Strength and Naltrexone Dose | 83.4 units on a scale | Standard Error 1.7 |
| Naltrexone (25mg) + Marijuana (3.27%THC) | Change in Mean Psychomotor Task Performance as a Function of Marijuana Strength and Naltrexone Dose | 83.5 units on a scale | Standard Error 1.6 |
| Naltrexone (50mg) + Marijuana (0.0%THC) | Change in Mean Psychomotor Task Performance as a Function of Marijuana Strength and Naltrexone Dose | 83.6 units on a scale | Standard Error 1.8 |
| Naltrexone (50mg) + Marijuana (3.27%THC) | Change in Mean Psychomotor Task Performance as a Function of Marijuana Strength and Naltrexone Dose | 82.1 units on a scale | Standard Error 1.4 |
| Naltrexone (100mg) + Marijuana (0.0%THC) | Change in Mean Psychomotor Task Performance as a Function of Marijuana Strength and Naltrexone Dose | 82.1 units on a scale | Standard Error 1.6 |
| Naltrexone (100mg) + Marijuana (3.27%THC) | Change in Mean Psychomotor Task Performance as a Function of Marijuana Strength and Naltrexone Dose | 83.0 units on a scale | Standard Error 1.7 |
Primary
Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose.
All subjective effects were measured using visual analog scales (VAS), a series of 100 mm long lines labeled 'not at all' at one end (0 mm) and 'extremely' at the other end (100 mm). Participants were instructed to rate their subjective experiences on the line according to how they felt at that particular moment. Subjective assessments included measures of perceived marijuana strength, marijuana high, good effects of marijuana, and how much marijuana was liked. Marijuana's effects were determined by comparing the active and inactive marijuana conditions when paired with the placebo naltrexone condition (one comparison). Naltrexone's intrinsic effects were assessed by comparing placebo and each active dose of naltrexone (12, 25, 50, and 100 mg) under the inactive marijuana condition (four comparisons). Finally, the active marijuana- placebo naltrexone condition was compared to the active marijuana-active naltrexone conditions (four comparisons)
Time frame: Baseline compared to 6 week timepoint
Population: Data from 29 participants were included in this analysis.
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Placebo + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Marijuana Strength | 8.0 units on a scale | Standard Deviation 0.8 |
| Placebo + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings High | 4.1 units on a scale | Standard Deviation 0.7 |
| Placebo + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Good Effect | 10.0 units on a scale | Standard Deviation 1.1 |
| Placebo + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Like Drug | 11.3 units on a scale | Standard Deviation 1.2 |
| Placebo + Marijuana (3.27% THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings High | 11.0 units on a scale | Standard Deviation 1.1 |
| Placebo + Marijuana (3.27% THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Marijuana Strength | 25.0 units on a scale | Standard Deviation 3.2 |
| Placebo + Marijuana (3.27% THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Like Drug | 35.0 units on a scale | Standard Deviation 5.3 |
| Placebo + Marijuana (3.27% THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Good Effect | 38.3 units on a scale | Standard Deviation 4.5 |
| Naltrexone (12mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings High | 3.7 units on a scale | Standard Deviation 0.6 |
| Naltrexone (12mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Marijuana Strength | 6.7 units on a scale | Standard Deviation 0.9 |
| Naltrexone (12mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Good Effect | 6.8 units on a scale | Standard Deviation 1.2 |
| Naltrexone (12mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Like Drug | 7.0 units on a scale | Standard Deviation 0.7 |
| Naltrexone (12mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Marijuana Strength | 34.0 units on a scale | Standard Deviation 2.1 |
| Naltrexone (12mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings High | 23.0 units on a scale | Standard Deviation 3.2 |
| Naltrexone (12mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Good Effect | 43.1 units on a scale | Standard Deviation 5.7 |
| Naltrexone (12mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Like Drug | 44.0 units on a scale | Standard Deviation 3.7 |
| Naltrexone (25mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Good Effect | 9.0 units on a scale | Standard Deviation 0.8 |
| Naltrexone (25mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings High | 3.0 units on a scale | Standard Deviation 0.6 |
| Naltrexone (25mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Like Drug | 9.3 units on a scale | Standard Deviation 1.2 |
| Naltrexone (25mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Marijuana Strength | 8.1 units on a scale | Standard Deviation 0.6 |
| Naltrexone (25mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Good Effect | 44.1 units on a scale | Standard Deviation 5 |
| Naltrexone (25mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings High | 20.4 units on a scale | Standard Deviation 2.2 |
| Naltrexone (25mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Marijuana Strength | 31.6 units on a scale | Standard Deviation 1.1 |
| Naltrexone (25mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Like Drug | 34.7 units on a scale | Standard Deviation 4.8 |
| Naltrexone (50mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings High | 4.0 units on a scale | Standard Deviation 0.3 |
| Naltrexone (50mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Good Effect | 10.2 units on a scale | Standard Deviation 1.1 |
| Naltrexone (50mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Like Drug | 10.3 units on a scale | Standard Deviation 0.5 |
| Naltrexone (50mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Marijuana Strength | 9.7 units on a scale | Standard Deviation 0.7 |
| Naltrexone (50mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Marijuana Strength | 36.2 units on a scale | Standard Deviation 2.3 |
| Naltrexone (50mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Like Drug | 38.0 units on a scale | Standard Deviation 6.6 |
| Naltrexone (50mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings High | 22.2 units on a scale | Standard Deviation 1.7 |
| Naltrexone (50mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Good Effect | 42.2 units on a scale | Standard Deviation 4.2 |
| Naltrexone (100mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Like Drug | 11.4 units on a scale | Standard Deviation 1.2 |
| Naltrexone (100mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Marijuana Strength | 10.1 units on a scale | Standard Deviation 0.9 |
| Naltrexone (100mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Good Effect | 12.5 units on a scale | Standard Deviation 0.9 |
| Naltrexone (100mg) + Marijuana (0.0%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings High | 3.9 units on a scale | Standard Deviation 0.3 |
| Naltrexone (100mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Good Effect | 44.0 units on a scale | Standard Deviation 4.8 |
| Naltrexone (100mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Marijuana Strength | 34.5 units on a scale | Standard Deviation 1.4 |
| Naltrexone (100mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings Like Drug | 44.0 units on a scale | Standard Deviation 6 |
| Naltrexone (100mg) + Marijuana (3.27%THC) | Change in Mean Subjective Mood Scores as a Function of Marijuana Strength and Naltrexone Dose. | Mean VAS ratings High | 21.3 units on a scale | Standard Deviation 2.4 |