Effects of oral THC maintenance on smoked marijuana self-administration

ENGLISH :
Studies have shown that the delta9-tetrahydrocannabinol (delta9-THC) concentration in marijuana cigarettes is an important factor for the maintenance of marijuana self-administration. Yet, the impact of oral delta9-THC treatment on marijuana self-administration is unknown. Because other agonist therapies have been demonstrated to be effective for the treatment of substance use disorders, the objective of this study was to evaluate the influence of oral delta9-THC maintenance on choice to self administer smoked marijuana. During this 18-day residential study, 12 healthy research volunteers received one of three doses of oral delta9-THC capsules (0, 10, 20 mg QID) for 3 consecutive days, followed by 3 consecutive days of matching placebo. The order of active delta9-THC administration was counterbalanced. Each morning, except on days 6, 12, and 18, participants smoked the `sample' marijuana cigarette (1.8% delta9-THC w/w) and received a $2 voucher (redeemable for cash at study's end). Following the sample, volunteers participated in a four- trial choice procedure during which they had the opportunity to self administer either the dose of marijuana they sampled that morning or to receive the $2 voucher. Relative to placebo D9-THC maintenance, participants' choice to self-administer marijuana was not significantly altered by either of the two active delta9-THC maintenance conditions. Some `positive' subjective drug-effect ratings following the sample marijuana cigarette were reduced: by day 3 of active oral delta9-THC maintenance, participants' rating of `Good Drug Effect' and `High' were significantly decreased. Smoked marijuana-related total daily caloric intake was not significantly altered under any maintenance conditions. Finally, the effects of smoked marijuana on psychomotor task performance were only minimally affected by oral delta9-THC maintenance. These data indicate that participants' choice to self-administer marijuana was unaltered by the oral delta9-THC dosing regimen used in the present investigation. (Review's abstract.)