Cannabinoid treatment of opiate addiction

Opioid abuse is a growing global problem. Current therapies for opioid abuse target withdrawal symptoms and have several adverse side effects. There are no treatments to address opioid-induced neural adaptations associated with abuse and addiction. Preclinical research demonstrates interactions between the endogenous opioid and cannabinoid systems, suggesting that cannabinoids may be used to treat opioid addiction and dependence. The aim of this review is to assess how cannabinoids affect behavioural and molecular measures of opioid dependence and addiction-like behaviour in animal models. It appears that cannabidiol and cannabinoid receptor 1 (CB1R) antagonists have potential for treating drug-craving and drug-seeking behaviour, based on evidence from preclinical animal models. Ligands which inhibit the action of cannabinoid degradation enzymes also show promise in reducing opioid withdrawal symptoms and opioid self-administration in rodents. Agonists of CB1R could be useful for treating symptoms of opioid withdrawal; however, the clinical utility of these drugs is limited by side effects, the potential for cannabinoid addiction and an increase in opiate tolerance induced by cannabinoid consumption. The mechanisms by which cannabinoids reduce opioid addiction-relevant behaviours include modulation of cannabinoid, serotonin, and dopamine receptors, as well as signalling cascades involving ERK-CREB-BDNF and peroxisome proliferator-activated receptor-α. Identifying the receptors involved and their mechanism of action remains a critical area of future research.