Medical Marijuana and Opioids (MEMO) Study: protocol of a longitudinal cohort study to examine if medical cannabis reduces opioid use among adults with chronic pain

INTRODUCTION: In the USA, opioid analgesic use and overdoses have increased dramatically. One rapidly expanding strategy to manage chronic pain in the context of this epidemic is medical cannabis. Cannabis has analgesic effects, but it also has potential adverse effects. Further, its impact on opioid analgesic use is not well studied. Managing pain in people living with HIV is particularly challenging, given the high prevalence of opioid analgesic and cannabis use. This study’s overarching goal is to understand how medical cannabis use affects opioid analgesic use, with attention to Δ9-tetrahydrocannabinol and cannabidiol content, HIV outcomes and adverse events. METHODS AND ANALYSES: We are conducting a cohort study of 250 adults with and without HIV infection with (a) severe or chronic pain, (b) current opioid use and (c) who are newly certified for medical cannabis in New York. Over 18 months, we collect data via in-person visits every 3 months and web-based questionnaires every 2 weeks. Data sources include: questionnaires; medical, pharmacy and Prescription Monitoring Program records; urine and blood samples; and physical function tests. Using marginal structural models and comparisons within participants’ 2-week time periods (unit of analysis), we will examine how medical cannabis use (primary exposure) affects (1) opioid analgesic use (primary outcome), (2) HIV outcomes (HIV viral load, CD4 count, antiretroviral adherence, HIV risk behaviours) and (3) adverse events (cannabis use disorder, illicit drug use, diversion, overdose/deaths, accidents/injuries, acute care utilisation). ETHICS AND DISSEMINATION: This study is approved by the Montefiore Medical Center/Albert Einstein College of Medicine institutional review board. Findings will be disseminated through conferences, peer-reviewed publications and meetings with medical cannabis stakeholders. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Registry (NCT03268551); Pre-results.