Antagonist-Elicited Cannabis Withdrawal

Summary

Background: Rimonabant, a CB1 receptor antagonist, blocks effects of cannabinoids and, in dependent animals, elicits cannabinoid withdrawal. No studies have examined rimonabantelicited cannabis withdrawal in humans.

Goals: (1) Determine the lowest single dose of oral rimonabant that elicits measurable cannabinoid withdrawal. (2) Characterize cognitive performance, subjective state, physiological condition, and regional brain activation (measured by functional magnetic resonance imaging \[fMRI\]) during acute and chronic administration of oral delta 9-tetrahydrocannabinol (THC) and during cannabis withdrawal. (3) Characterize the pharmacokinetics of oral THC and metabolites in body fluids and hair and of rimonabant in plasma.

Subject Population: Up to 60 completing cannabis users aged 18-45 (up to 24 in Experiment I, 36 in Experiment II) and 18 completing non-drug-using controls (Experiment II). Enrollment target is 82% Caucasian, 14% African American, 4% other; 9% Hispanic; 35% women.

Experimental Design and Methods: Experiment I: In this within-subject, randomized, double-blind, dose-escalation study, six participants receive 7 days of THC (40-120 mg/day). On Day 8, five participants receive 20 mg rimonabant; one receives placebo. If withdrawal criteria (greater than or equal to 150% or 2.5-fold increase in selected visual-analog scales) are not met in all five participants receiving rimonabant, separate groups of six are similarly treated with 40, 60 or 80 mg rimonabant, if necessary. The PI and MRP will submit all adverse events and relevant cardiovascular and scientific data to the IRB at the completion of each rimonabant dose panel. When the extramural NIDA DSMB is in place, it will review all data collected to date and develop and implement a monitoring plan, including review on completion of each dose cohort. DSMB recommendations will be reviewed by the Sponsor, Clinical Director and IRB before proceeding to the next dose cohort. In addition, if any subject has an intolerable adverse event (ie, an adverse event leading to study discontinuation) or serious adverse event in response to rimonabant on Day 8, the blind for that subject will be broken, and a report sent to the Sponsor, the extramural NIDA DSMB when in place and the IRB for discussion.

Experiment II: In this randomized, placebo-controlled, double-blind study, 36 participants receive 7 days of THC (40-120 mg/day). On Day 8, 18 participants receive rimonabant dose determined in Experiment I to elicit cannabis withdrawal; 18 participants receive placebo rimonabant to evaluate spontaneous cannabis withdrawal. Cognitive, psychological, physiological and hormonal measures are monitored to determine onset, magnitude, and duration of THC intoxication and withdrawal and to correlate with THC and rimonabant pharmacokinetics. Changes in blood oxygen level-dependent (BOLD) signal are determined with five fMRI scans throughout the study. Eighteen non-drug-using controls undergo scanning and cognitive testing at similar intervals.

Risks and Benefits: The proposed doses of THC and rimonabant have been well tolerated in other studies. The most common side effects of oral THC are sedation, cognitive impairment, euphoria, poor coordination, tachycardia, and hypotension. Spontaneous withdrawal from cannabis is mild and medically benign. Experience with other drugs suggests that antagonist-elicited cannabis withdrawal may have an earlier onset and greater intensity than spontaneous cannabis withdrawal. There are no clinical benefits to participants. Scientific benefits are greater understanding of cannabis intoxication, tolerance, and withdrawal and of the role of rimonabant in eliciting cannabis withdrawal.

Conditions

• Cannabis
• Dependence

Interventions

DRUG

THC

DRUG

Rimonobant

DRUG

Rimonabant

Sponsors & Collaborators

• National Institute on Drug Abuse (NIDA)

  lead NIH

Study Design

Allocation

RANDOMIZED

Purpose

OTHER

Masking

DOUBLE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

45 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2006-04-16

Primary Completion

2010-01-11

Completion

2010-01-11

Countries

• United States

Study Locations