Vilazodone Treatment for Marijuana Dependence

Phase 2

Completed

Brief Summary: Marijuana is the most commonly used illicit drug, yet few clinical trials have evaluated pharmacotherapy treatments for marijuana dependence. This study will evaluate the efficacy of vilazodone for reducing marijuana use in marijuana-dependent adults. A contingency management intervention (CM)and motivational enhancement therapy (MET)will be incorporated to encourage study engagement and retention, and genomic DNA will be extracted to characterize subjects according to polymorphisms of genes potentially relevant to the activity of vilazodone. It is hypothesized that vilazodone combined with MET and CM will reduce the percent of marijuana-positive urine drug screen results in marijuana-dependent individuals as compared to a placebo treatment combined with MET and CM.

Detailed Description: The purpose of this study is to determine if the medication vilazodone is effective in helping frequent marijuana smokers cut down or stop using marijuana. Vilazodone is FDA approved for the treatment of depression- in this study, vilazodone's effect on marijuana dependence is being investigated.

Participation in the study takes 10 visits over a period of approximately two to three months. The first visit is a screening visit to determine if participants are eligible to participate. After the initial assessment visit, the weekly visits take about 30 minutes, with the exception of three therapy sessions which take approximately 60-90 minutes. The three therapy sessions will focus on participant's marijuana use and reasons they may have for stopping or cutting down on use. After completing an initial therapy session, participants will be randomly selected to receive the study medication, either vilazodone or placebo (a capsule that does not contain any active medication). Participants will have weekly study visits with a clinician. At each study visit, they will be asked to fill out forms and answer specific questions concerning their substance use, anxiety symptoms, and feelings in general. They will be providing urine samples to check for illegal drugs of abuse including marijuana and other drugs. They will also have blood samples drawn during to determine if you are taking the medication as directed.

Recruitment & Eligibility

Inclusion Criteria

Must meet DSM-IV criteria for marijuana dependence
Must be between the ages of 18 and 65 years old
If female and of childbearing potential, must agree to use acceptable method of birth control for duration of the trial.
Cannabis-positive urine drug screen at screening
Must consent to random assignment
Must be able to read and provide informed consent

Exclusion Criteria

Women who are pregnant, nursing, or plan to become pregnant during course of study
Must not have a history of or current psychotic disorder, bipolar disorder, or eating disorder
Must not pose a current suicidal or homicidal risk
Must not have evidence or history of serious medical disease
Must not require concomitant therapy with psychotropic medication or CYP3A4 inhibitors
Must not be currently dependent on other substances, with the exception of nicotine;
Patients who, in the investigator's opinion, would be unable to comply with study procedures or assessments

Arm && Interventions

Group	Intervention	Description
Placebo	Placebo	Flexible dose up to 40 mg capsule daily
Vilazodone	Vilazodone	Flexible dose up to 40 mg capsule daily

Primary Outcome Measures

Name	Time	Method
Percent Marijuana-negative Urine Drug Screens (UDS)	8 weeks	Participants submitted a urine sample weekly. Percentage of marijuana negative urine samples were calculated per group.

Secondary Outcome Measures

Name	Time	Method
Weekly Cannabis Use Sessions	8 weeks	Self-report of weekly cannabis use sessions was measured using the Time Line Followback, a calendar-based instrument designed to assess substance consumption.
Marijuana Craving and Withdrawal	8 weeks	The Marijuana Craving Questionnaire (MCQ) is intended to measure marijuana craving in adults. It measures symptoms on four subscales: expectancy, purposefulness, emotionality, and compulsivity. The scale rates individual items from 1 (least craving) - 7 (most craving) with a composite scoring range of 12-84 and possible subscale scoring range of 3-21. It was administered weekly to all participants. Reported here is the mean MCQ purposefulness subscale score across 8 weeks.