Quetiapine Pharmacotherapy for Cannabis Dependence
Status:
Completed
Trial end date:
2017-04-30
Target enrollment:
Participant gender:
Summary
Despite a benign public perception, marijuana use disorders represent a significant public
health problem. The development of safe and effective pharmacotherapies for marijuana
dependence is an important unmet public health need. Quetiapine, an effective atypical
antipsychotic that acts by blocking serotonin type 2A, dopamine type 2, histamine type 1, and
adrenergic receptors, is a promising treatment for substance use disorders. In animal models,
quetiapine blocks the enhancement of reward by cocaine, which is likely due to its actions on
both dopamine and non-dopamine neurotransmission. Clinical studies of quetiapine have shown
benefit for the treatment of alcohol and cocaine use disorders.
Conceptually, the clinically prominent effects of quetiapine, namely sedation, anxiolysis,
mood stabilization and appetite stimulation, are a good match for the symptoms of marijuana
withdrawal. Most importantly, an open-label dose-finding study of quetiapine for the
treatment of marijuana dependence conducted by our research group determined that quetiapine
was well-tolerated and associated with reductions in marijuana use indicating that it is a
promising agent deserving of further study in marijuana-dependent outpatients.
The proposed research project is a randomized double-blind placebo-controlled clinical trial
to evaluate the efficacy of quetiapine for the treatment of marijuana dependence over a
12-week period. All participants will receive Medical Management, a medication adherence
focused psychosocial intervention that facilitates compliance with study medication and other
study procedures, promotes abstinence from marijuana and other substances, and encourages
mutual-support group attendance. All participants will receive voucher incentives for
compliance with study visit attendance, returning study medication bottles, and completing
other study procedures, with the objective of achieving a highly compliant sample. The goal
of this phase II clinical trial is to build on our promising open-label pilot study results
and examine the efficacy of quetiapine on participants' marijuana consumption under
placebo-controlled double-blind conditions using an abstinence-initiation model, where
participants will be using marijuana regularly at study entry, reduce their use, and then
achieve abstinence. The specific aims of the projects are to determine whether quetiapine is
superior to placebo in 1) reducing marijuana use and 2) achieving abstinence.