Quantifying unused opioids following emergency and ambulatory care: A systematic review and meta-analysis

Objective To quantify unused opioids among adult and pediatric patients discharged from the emergency department (ED) or ambulatory care settings with a prescription for acute pain. Methods We searched MEDLINE, Embase, CINHAL, PsycINFO, the Cochrane Library, and the gray literature from inception to April 29, 2021. We included observational studies in which any patient with an acutely painful condition received a prescription for an opioid on discharge from an outpatient care setting, and unused opioids were quantified. Two reviewers screened records for eligibility, extracted data, and conducted the quality assessment. Where possible, we pooled data and otherwise described the results of studies narratively. Total unused prescriptions were synthesized using a weighted average. Random effects models were used, and heterogeneity was measured by the I-2 statistic. Our primary outcome was the quantity of unused opioid medication available after receiving a prescription for acute pain. Secondary outcomes were the proportion of patients with unused opioids following a prescription, the proportion of patients using no opioids, morphine equivalents of unused opioids, and factors associated with leftover opioids. Results In this systematic review and meta-analysis of 9 studies in emergency and ambulatory care settings, 59.6% of prescribed opioids remained unused; pediatric patients had 69.3% of their prescriptions remaining, compared to 54.6% among adult patients. The highest proportion of unused opioids was found following dental extractions (82.6%). Conclusions and Relevance More than 50% of opioids remain unused following prescriptions for acute pain. Responsible prescribing must be accompanied by education on safer use, storage, and disposal.