Improving Substance Use and Clinical Outcomes in Heavy Cannabis Users With Quetiapine
Condition: Cannabis Dependence
MeSH terms: Substance-Related Disorders; Marijuana Abuse
Study type: Interventional
Phase: Phase 4

Summary: 
      Cannabis is the most used illicit substance in the United States. Previous studies suggest
      that atypical antipsychotics decrease the frequency and the amount of substance use in
      subjects with and without psychotic illness. So far, there are no controlled studies
      assessing the effectiveness of atypical antipsychotics for decreasing cannabis and other
      substance use in individuals with cannabis use disorders. The investigators postulate that
      the atypical antipsychotic quetiapine ER is an effective agent for improving substance use
      outcomes in subjects with cannabis use disorders. In this pilot study, the investigators will
      test this hypothesis in heavy cannabis users (i.e., individuals who are cannabis dependent
      and smoke three times or more per week). Because 50% of these heavy cannabis users report
      histories of psychotic experiences (i.e., attenuated positive symptoms) while smoking and are
      at risk for recurring psychotic symptoms, the investigators will focus this pilot clinical
      trial on this subgroup of cannabis users in order to increase the risk/benefit ratio of this
      study and target a population that may also benefit from the antipsychotic effect of
      quetiapine ER. Considering the lack of controlled studies assessing the efficacy of atypical
      antipsychotics in heavy cannabis users, assessing the effectiveness of an atypical
      antipsychotic medication on substance use and clinical outcomes in this population is
      critical for improving the prognosis of these individuals.

      Thus, the aims of this randomized, double-blind, placebo-controlled study are to assess the
      efficacy of an atypical antipsychotic (quetiapine ER) in 120 subjects with cannabis
      dependence, a recent history (within a year) of attenuated psychotic symptoms, and using
      cannabis 3 times or more per week for: (1) decreasing the use of cannabis and other
      substances; and (2) preventing the recurrence of psychotic experiences. The investigators
      will also assess the effects of quetiapine ER on craving and mood, and its tolerability. This
      project will be a 12-week, randomized, double-blind, placebo-controlled study with quetiapine
      ER and it will include a comprehensive assessment of symptoms, substance use, and side
      effects.

      This study will benefit the field by providing unique data on the relative efficacy and
      tolerability of treatment with atypical antipsychotics in heavy cannabis users with a
      vulnerability to psychosis. This study will be the basis for future studies assessing the
      long-term efficacy and tolerability of atypical antipsychotics in individuals with cannabis
      use disorders.
    


Intervention name(s): Behavioral Intervention
Intervention type(s): Behavioral
Intervention description(s): Substance-related
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: Quetiapine; Psychotic experiences; Cannabis dependence; Craving; Mood; Substance use