Conditions: Marijuana Use
Keywords: Naltrexone Smoked Marijuana
Allocation: RANDOMIZED | Intervention model: SINGLE_GROUP
Enrollment: 49
Healthy volunteers: yes

Brief summary:
The purpose of this study is to determine if the subjective effects of marijuana will be decreased by low-doses (\< 25 mg) of naltrexone and increased by high-doses (\> 50 mg) of naltrexone.

Detailed description:
Laboratory animal studies demonstrate that endogenous cannabinoids and opioids are closely inter-related. We have completed a series of studies in marijuana smokers showing that a clinically-utilized dose of naltrexone (50 mg) enhanced the reinforcing and subjective effects of orally-administered tetrahydrocannabinol (THC), while a low naltrexone dose (12 mg) blunted the effects of THC. A better understanding of the effects of a range of naltrexone doses in combination with smoked marijuana has important implications for the following reasons: (1) Alcohol- and opioid-dependent patients receive high doses of naltrexone (50-150 mg), which may increase the abuse liability of marijuana, (2) Low-dose naltrexone blunts THC's intoxicating effects, suggesting potential utility as a treatment medication for marijuana dependence. This study will determine if naltrexone (0, 12, 25, 50, 100 mg) administration 45 min prior to marijuana administration (0, 3.27% THC) alters marijuana's subjective, cognitive or physiological effects. Marijuana smokers will spend approximately 5h/day for a total of 10 days in the outpatient laboratory. Participants will visit the outpatient laboratory 2-3 times per week, with a minimum 48-hr interval between sessions to allow for naltrexone clearance. These data will provide important information regarding the clinical use of naltrexone.

Arms:
arm 1: During each session, one capsule containing placebo was administered to the participant in a size 00 opaque capsule with lactose filler. A marijuana cigarette (0% THC; ca. 800 mg) provided by the National Institute on Drug Abuse, was administered 45 minutes post capsule administration. arm 2: During each session, one capsule containing placebo was administered to the participant in a size 00 opaque capsule with lactose filler. A marijuana cigarette (3.27% THC; ca. 800 mg) provided by the National Institute on Drug Abuse, was administered 45 minutes post capsule administration. arm 3: During each session, one capsule containing naltrexone (12 mg) was administered to the participant in a size 00 opaque capsule with lactose filler. A marijuana cigarette (0% THC; ca. 800 mg) provided by the National Institute on Drug Abuse, was administered 45 minutes post capsule administration. arm 4: During each session, one capsule containing naltrexone (12 mg) was administered to the participant in a size 00 opaque capsule with lactose filler. A marijuana cigarette (3.27% THC; ca. 800 mg) provided by the National Institute on Drug Abuse, was administered 45 minutes post capsule administration. arm 5: During each session, one capsule containing naltrexone (25 mg) was administered to the participant in a size 00 opaque capsule with lactose filler. A marijuana cigarette (0% THC; ca. 800 mg) provided by the National Institute on Drug Abuse, was administered 45 minutes post capsule administration. arm 6: During each session, one capsule containing naltrexone (25 mg) was administered to the participant in a size 00 opaque capsule with lactose filler. A marijuana cigarette (3.27% THC; ca. 800 mg) provided by the National Institute on Drug Abuse, was administered 45 minutes post capsule administration. arm 7: During each session, one capsule containing naltrexone (50 mg) was administered to the participant in a size 00 opaque capsule with lactose filler. A marijuana cigarette (0% THC; ca. 800 mg) provided by the National Institute on Drug Abuse, was administered 45 minutes post capsule administration. arm 8: During each session, one capsule containing naltrexone (50 mg) was administered to the participant in a size 00 opaque capsule with lactose filler. A marijuana cigarette (3.27% THC; ca. 800 mg) provided by the National Institute on Drug Abuse, was administered 45 minutes post capsule administration. arm 9: During each session, one capsule containing naltrexone (100 mg) was administered to the participant in a size 00 opaque capsule with lactose filler. A marijuana cigarette (0% THC; ca. 800 mg) provided by the National Institute on Drug Abuse, was administered 45 minutes post capsule administration. arm 10: During each session, one capsule containing naltrexone (100 mg) was administered to the participant in a size 00 opaque capsule with lactose filler. A marijuana cigarette (3.27% THC; ca. 800 mg) provided by the National Institute on Drug Abuse, was administered 45 minutes post capsule administration.

Interventions: intervention 1: Placebo + Inactive Marijuana (0% THC) intervention 2: Placebo + Active Marijuana (3.27% THC) intervention 3: Naltrexone 12 Mg+ Active Marijuana (3.27% THC) intervention 4: Naltrexone 25 Mg + Active Marijuana (3.27% THC) intervention 5: Naltrexone 50 Mg+ Active Marijuana (3.27% THC) intervention 6: Naltrexone 100 Mg+ Active Marijuana (3.27% THC) intervention 7: Naltrexone 12 Mg + Inactive Marijuana (0% THC) intervention 8: Naltrexone 25 Mg + Inactive Marijuana (0% THC) intervention 9: Naltrexone 50 Mg + Inactive Marijuana (0% THC) intervention 10: Naltrexone 100 Mg + Inactive Marijuana (0% THC)
Intervention descriptions: intervention 1: One capsule containing placebo was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before marijuana administration. intervention 2: One capsule containing placebo was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before administration of a marijuana cigarette containing 3.27% THC (ca. 800 mg) provided by the National Institute on Drug Abuse. intervention 3: One capsule containing 12mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before active marijuana administration. intervention 4: One capsule containing 12mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before active marijuana administration. intervention 5: One capsule containing 25mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before marijuana administration. intervention 6: One capsule containing 50mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before marijuana administration. intervention 7: One capsule containing 12mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before inactive marijuana administration. intervention 8: One capsule containing 25mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before inactive marijuana administration. intervention 9: One capsule containing 50mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before inactive marijuana administration. intervention 10: One capsule containing 100mg Naltrexone was administered to the participant in a size 00 opaque capsules with lactose filler 45 minutes before inactive marijuana administration.

Protocol document: