Antagonist-Elicited Cannabis Withdrawal

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 subjec