Grant: Project Grant

Approximately 20% of Canadian and U.S. adults live with chronic pain. Despite a downturn in the number of opioid prescriptions, U.S. data from 2017 suggests a significant number are dispensed. Long-term use of opioid medication can lead to loss of pain-relieving effectiveness and the development of dependence and withdrawal symptoms that make stopping administration difficult even when pain is poorly managed. Misuse of opioids prescribed for chronic pain occurs in up to 29% of patients with up to 12% developing opioid use disorder (OUD). Indeed, 80% of heroin users may have first misused prescription opioids. High rates of opioid prescribing, along with the emergence of strong synthetic opioids and the development of addiction has led to high overdose death rates and economic costs in North America. Research is needed to transform the way we identify, monitor and treat OUD. The proposed project aims to establish whether there are abnormalities in the brains endogenous cannabinoid (endocannabinoid) system (eCS) in chronic pain patients with OUD. There are well-established links between the brains opioid system (the site at which opioid medication works) and the eCS. For instance, these systems interact in pain and reward processing. There is also growing awareness that the eCS plays an important role in drug reward and addictive behaviours. Despite this, we still know very little about the eCS in those with OUD. Fatty acid amide hydrolase (FAAH) is an important enzyme within the eCS because it is responsible for the breakdown and inactivation of one of the main eCS neurotransmitters, anandamide. Reduced FAAH levels have previously been found in alcohol and cannabis use disorders. We will use positron emission tomography imaging, which uses small amounts of radioactive materials and specialized cameras, to investigate whether FAAH levels are lower in the brains of chronic pain patients with OUD compared to those without problem opioid use and healthy controls.