Opioid prescribing requirements to minimize unused medications after an emergency department visit for acute pain: a prospective cohort study

Background: Unused opioid prescriptions can be a driver of opioid misuse. Our objective was to determine the optimal quantity of opioids to prescribe to patients with acute pain at emergency department discharge, in order to meet their analgesic needs while limiting the amount of unused opioids. Methods: In a prospective, multicentre cohort study, we included consecutive patients aged 18 years and older with an acute pain condition present for less than 2 weeks who were discharged from emergency department with an opioid prescription. Participants completed a pain medication diary for real-time recording of quantity, doses, and names of all analgesics consumed during a 14-day follow-up period. Results: We included 2240 participants, who had a mean age of 51 years; 48% were female. Over 14 days, participants consumed a median of 5 (quartiles, 1-14) morphine 5 mg tablet equivalents, with significant variation across pain conditions (p < 0.001). Most opioid tablets prescribed (63%) were unused. To meet the opioid need of 80% of patients for 2 weeks, we found that those experiencing renal colic or abdominal pain required fewer opioid tablets (8 morphine 5 mg tablet equivalents) than patients who had fractures (24 tablets), back pain (21 tablets), neck pain (17 tablets), or other musculoskeletal pain (16 tablets). Interpretation: Two-thirds of opioid tablets prescribed at emergency department discharge for acute pain were unused, whereas opioid requirements varied significantly based on the cause of acute pain. Smaller, cause-specific opioid prescriptions could provide adequate pain management while reducing the risk of opioid misuse.