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Treatment of Schizophrenia and Comorbid Cannabis Use Disorder: Comparing Clozapine to Treatment-as-Usual

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT00498550
Recruitment Status : Completed
First Posted : July 10, 2007
Results First Posted : January 19, 2012
Last Update Posted : March 13, 2019
National Institute on Drug Abuse (NIDA)
University of Missouri, Kansas City
VA Medical Center-West Los Angeles
University of South Carolina
Information provided by (Responsible Party):
Alan Green, Dartmouth-Hitchcock Medical Center

Brief 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.

Condition or disease Intervention/treatment Phase
Schizophrenia Dual Diagnosis Schizoaffective Disorder Psychotic Disorder Cannabis Abuse Drug: Clozapine Drug: Treatment as usual Phase 4

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.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 31 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary Purpose: Treatment
Official Title: Cannabis and Schizophrenia: Effects of Clozapine
Study Start Date : October 2000
Actual Primary Completion Date : March 2009
Actual Study Completion Date : March 2009

Resource links provided by the National Library of Medicine

Drug Information available for: Clozapine

Arm Intervention/treatment
Experimental: Clozapine
Clozapine, Clozaril
Drug: Clozapine
Clozapine up to 550mg per day
Other Name: Clozaril

Active Comparator: Treatment as usual
Treatment as usual with any antipsychotic other than Clozapine.
Drug: Treatment as usual
Remain on pre-study antipsychotic treatment

Primary Outcome Measures :
  1. Average Over Time of Intensity of Cannabis Use (Used to Evaluate Treatment Efficacy) [ Time Frame: Week 1 to week 12 ]
    Intensity of cannabis use is obtained for each week retrospectively as the number of joints smoked during the prior week (assessed by the Timeline Followback Scale). Mixed models are used to obtain estimates of efficacy from the partial data provided by each subject while adherent to assigned treatment (under the 'missing at random' assumption). The 'explanatory' estimands (target of the mixed model estimation) are defined in terms of population quantities that would have occurred had all subjects remained on assigned treatment throughout the study. The point estimate for each arm is reported under Number.

Information from the National Library of Medicine

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, Learn About Clinical Studies.

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Ages Eligible for Study:   18 Years to 65 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Meets Diagnostic and Statical Manual of Mental Disorders IV (DSM-IV) diagnostic criteria for schizophrenia or schizoaffective disorder
  • Meets diagnostic criteria for marijuana use disorder, as determined by a rating of 3 or higher on the Drug Use Scale (Abuse or Dependence)
  • Used marijuana on 5 or more days during the 3 weeks prior to study entry
  • Taking any oral antipsychotic other than clozapine in the month prior to study entry. (Patients may take a second oral antipsychotic medication, if approved by the Medication Adjustment Group)
  • If female, willing to use effective contraception throughout the study

Exclusion Criteria:

  • Unable to take clozapine for medical reasons, including previous clozapine-induced granulocytopenia, myeloproliferative disorder, white blood cell count less than 3500/mm3, or history of seizures
  • Currently taking clozapine
  • Currently taking other psychotropic medications for the treatment of substance use (e.g., disulfiram, naltrexone, acamprosate, inderol, tegretol, topiramate, and pramipexole)
  • Participated in a clinical trial of an investigational drug within 30 days of study entry
  • Currently participating in a psychosocial intervention clinical trial
  • Has medical or legal problems that may entail a jail or hospital stay during the study
  • Has a developmental disability that would make study participation difficult
  • Currently enrolled in a live-in treatment program for substance use disorders
  • Pregnant or plans to become pregnant during the study

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT00498550

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United States, California
Los Angeles, California, United States, 90073
United States, Missouri
University Missouri
Kansas City, Missouri, United States, 64108
United States, New Hampshire
Mental Health Center of Greater Manchester
Manchester, New Hampshire, United States, 03101
United States, South Carolina
University South Carolina
Columbia, South Carolina, United States, 29203
Sponsors and Collaborators
Dartmouth-Hitchcock Medical Center
National Institute on Drug Abuse (NIDA)
University of Missouri, Kansas City
VA Medical Center-West Los Angeles
University of South Carolina
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Principal Investigator: Alan Green, MD Dartmouth-Hitchcock Medical Center
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Responsible Party: Alan Green, Principal Investigator, Dartmouth-Hitchcock Medical Center Identifier: NCT00498550    
Obsolete Identifiers: NCT00149955
Other Study ID Numbers: R01DA013196 ( U.S. NIH Grant/Contract )
First Posted: July 10, 2007    Key Record Dates
Results First Posted: January 19, 2012
Last Update Posted: March 13, 2019
Last Verified: February 2019
Keywords provided by Alan Green, Dartmouth-Hitchcock Medical Center:
Dual Diagnosis
Substance Abuse
Cannabis Abuse
Additional relevant MeSH terms:
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Marijuana Abuse
Psychotic Disorders
Mental Disorders
Pathologic Processes
Schizophrenia Spectrum and Other Psychotic Disorders
Substance-Related Disorders
Chemically-Induced Disorders
Serotonin Antagonists
Serotonin Agents
Neurotransmitter Agents
Molecular Mechanisms of Pharmacological Action
Physiological Effects of Drugs
Antipsychotic Agents
Tranquilizing Agents
Central Nervous System Depressants
Psychotropic Drugs
GABA Antagonists
GABA Agents