Skip to content

Interaction between naltrexone and oral THC in heavy marijuana smokers.

Margaret Haney, Adam Bisaga, Richard W Foltin

Psychopharmacology February 2003 DOI: 10.1007/s00213-002-1279-8 (opens in new tab)

Read Full Text
Relevant Not relevant

Study at a glance

AI-extracted from the abstract
Characteristics Controlled human laboratory study (three sub-studies) Peer reviewed
Sample size 23
Population Heavy marijuana smokers
Interventions Naltrexone THC Methadone
Dose naltrexone 0, 50 mg; THC 0, 15, 30 mg; methadone 5, 10 mg
Measures Good Drug Effect, Capsule Liking, drug choice test
Topics Cannabis
Key points Naltrexone pretreatment significantly increased many positive subjective effects of 30 mg oral THC, such as ratings of Good Drug Effect and Capsule Liking, and tended to increase THC's reinforcing effects in a drug choice test, while not altering plasma THC levels. The authors argue that in heavy marijuana smokers, oral THC's effects are enhanced rather than antagonized by opioid receptor blockade, contrary to animal studies suggesting opioid antagonists block cannabinoid reinforcement.

Abstract

Studies in non-human animals suggest that opioid antagonists block the reinforcing effects of cannabinoids. The present studies in humans investigated how naltrexone modulates (1) the subjective and physiological effects of oral THC in comparison to methadone, (2) the reinforcing effects of oral THC, and (3) plasma levels of oral THC. In study 1, marijuana smokers (n=9) received naltrexone (0, 50 mg) followed 30 min later by THC (0, 15, 30 mg) or methadone (5, 10 mg). Subjective effects, task performance, pupillary diameter, and cardiovascular parameters were measured repeatedly. In study 2a, marijuana smokers (n=23) were randomly assigned to one THC dose condition (0, 15 or 30 mg). One set of color-coded capsules containing THC and active naltrexone (50 mg) was given in one session, while another set of color-coded capsules containing THC and placebo naltrexone was given in another session. In the final three sessions, participants chose which color capsules they would receive. In study 2b, a subset of participants from study 2a (n=7) received naltrexone (0, 50 mg) 30 min prior to oral THC (30 mg) administration, and blood was drawn repeatedly. Pretreatment with naltrexone significantly increased many of the "positive" subjective effects of oral THC (30 mg) e.g. ratings of Good Drug Effect and Capsule Liking. Naltrexone tended to increase the reinforcing effects of oral THC (30 mg), as indicated by performance in a drug choice test. Naltrexone did not alter plasma THC levels. These studies demonstrate that naltrexone increases the subjective effects of oral THC. Thus, oral THC's effects are enhanced rather than antagonized by opioid receptor blockade in heavy marijuana smokers.

Comparable studies

Other experimental studies on cannabis, most cited first.

Study Year Design Participants
Smoked Cannabis' Psychomotor and Neurocognitive Effects in Occasional and Frequent Smokers Occasional (<2x/week) and frequent (≥4x/week) cannabis smokers 2015 Controlled within-subjects study n = 25
Dissociable effects of cannabis with and without cannabidiol on the human brain’s resting-state functional connectivity Healthy volunteers experienced with cannabis but not regular users 2019 Within-subjects experimental design n = 17
Which biological and self-report measures of cannabis use predict cannabis dependency and acute psychotic-like effects? Young cannabis users 2018 Observational study (naturalistic, within-subject counterbalanced design) n = 410
Cannabis Essential Oil: A Preliminary Study for the Evaluation of the Brain Effects Healthy volunteers 2018 Experimental study n = 5
Coming off cannabis: a cognitive and magnetic resonance imaging study in patients with multiple sclerosis Patients with multiple sclerosis who began using cannabis after disease onset, used it... 2019 Quasi-experimental study with odd-even allocation n = 40

Citations in the library

Cited by 8

and 3 more in the library

Cites 2

Related reading

Explore topics

Cannabis