Opioid prescribing and adverse events in opioid-naive patients treated by emergency physicians versus family physicians: a population-based cohort study

Background — Emergency physicians provide primary care to patients and often prescribe opioids for acutely painful self-limiting conditions. The objective of this study was to describe patterns of opioid prescribing by emergency physicians and family physicians and to explore the relation between setting of initiation of opioid treatment and adverse events over the subsequent 2 years. 

Methods — This was a population-based cohort study using administrative data from Ontario. Opioid-naive patients aged 15-64 years who received an opioid prescription for noncancer pain from an emergency or family physician between Apr. 1, 2008, and Mar. 31, 2012 were eligible for inclusion. 

Results — A total of 34 713 and 45 952 patients were initiated on an opioid by an emergency physicians and family physicians, respectively. Both emergency and family physicians most commonly prescribed codeine-containing products (58.9% and 79.6% of prescriptions, respectively); however, emergency physicians were twice as likely as family physicians to prescribe higher-potency opioids (morphine, oxycodone, hydromorphone, fentanyl, meperidine) (both combination and single-agent preparations) (40.6% v. 19.9%, ∆ = 20.7, 95% confidence interval [CI] 20.0-21.3). Compared to patients in the family physician group, those in the emergency physician group received significantly higher daily dosages, a higher proportion were initiated on a daily dosage of 100 mg of morphine equivalents (MEQs) or more, and had a hospital admission for opioid toxicity within 2 years (0.5% v. 0.3%, ∆ = 0.2%, 95% CI 0.1%-0.3%). A higher proportion of patients in the family physician group than in the emergency physician group had dosage escalation beyond 199 mg MEQs within 2 years (0.7% v. 0.1%, ∆ = 0.6%, 95% CI 0.5%-0.7%). 

Interpretation — Codeine was the most common opioid prescribed by emergency and family physicians. Compared to patients prescribed opioids by family physicians, those prescribed opioids by emergency physicians received higher initial daily dosages and had an increased likelihood of opioid toxicity.