Treatment of Schizophrenia and Comorbid Cannabis Use Disorder: Comparing Clozapine to Treatment-as-Usual
Condition: Schizophrenia; Dual Diagnosis; Schizoaffective Disorder; Psychotic Disorder; Cannabis Abuse
MeSH terms: Marijuana Abuse; Schizophrenia; Psychotic Disorders
Study type: Interventional
Phase: Phase 4

Summary: 
      Many individuals with schizophrenia also suffer from marijuana addiction. Clozapine, an
      atypical antipsychotic medication, may prove useful at preventing drug relapse in
      schizophrenic individuals who are seeking treatment for marijuana addiction. The purpose of
      this study is to compare the effectiveness of clozapine, vs. treatment-as-usual with other
      oral antipsychotics at reducing marijuana use in schizophrenic individuals.
    

Detailed description: 
      Individuals with schizophrenia have a high risk of becoming addicted to drugs; between 13 to
      42% of schizophrenics are addicted to marijuana. These individuals often have difficulties
      adhering to a substance abuse treatment program, and have an increased chance of marijuana
      relapse. Marijuana use by schizophrenics has also been associated with clinical
      exacerbations, noncompliance with antipsychotic medications, poor global functioning, and
      increased rehospitalization rates. While antipsychotic medications are often effective in
      controlling symptoms of schizophrenia, they are not always effective in preventing substance
      abuse. Clozapine, an atypical antipsychotic drug, is currently used to treat schizophrenia.
      Preliminary research has shown that clozapine is more successful at reducing drug relapse
      rates in individuals with schizophrenia, as compared to other antipsychotic medications,
      including olanzapine and risperidone. The purpose of this study is to compare the
      effectiveness of clozapine as compared to other oral antipsychotic treatment, including
      combinations of up to two antipsychotics, in reducing marijuana use in schizophrenic
      individuals.

      This study will enroll individuals with schizophrenia who are currently taking any oral
      antipsychotic other than clozapine, including those taking up to two oral antipsychotic, and
      who are also addicted to marijuana. The study will begin with a 1-week assessment phase,
      during which all participants will continue taking olanzapine or risperidone. Participants
      will undergo a physical examination and have blood drawn for laboratory tests. Information
      pertaining to their medical, psychiatric, and substance use history will also be collected.
      Urine tests and breathalyzers will be used to screen for the presence of alcohol and drugs.
      Following the assessment phase, participants will be randomly assigned to switch to clozapine
      or remain on their prestudy antipsychotic for 12 weeks. Participants remaining on their
      prestudy antipsychotic treatment will continue to receive the same dose for the entire study.
      Participants taking clozapine will initially receive a daily dose of 12.5 mg, which will be
      increased to a maximum of 400 mg per day, as tolerated. Study visits will take place once a
      week. At each visit, medication side effects, physical and psychological symptoms, substance
      use, treatment services received, and living situation will be assessed. Blood will be drawn
      for laboratory tests. Drug and alcohol levels will be monitored three times a week through
      urine and breathalyzer tests. Quality of life questionnaires will be administered once a
      month.
    

Intervention name(s): Clozapine; Treatment as usual
Intervention type(s): Drug; Drug
Intervention description(s): Clozapine up to 550mg per day; Remain on pre-study antipsychotic treatment
Other intervention name(s): Clozaril
Intervention MeSH terms: Clozapine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: Clozapine; Schizophrenia; Dual Diagnosis; Substance Abuse; Cannabis Abuse