Quantity of Opioids for Acute Pain and Limit Unused Medication

Introduction

Prescription opioid overdoses have quadrupled in the last 15 years, and are now the leading cause of accidental death, surpassing motor vehicle accidents. The drastic rise in opioid prescription rates in Canada and the US could be the driving force behind this higher mortality. It was shown that 71% of opioid misusers (i.e., intentional users for nonmedical purposes) received their drugs through the diversion of unused prescribed opioids (transfer of opioids to someone other than the holder of the initial prescription). Emergency department (ED) physicians are among the top opioid prescribers for patients under 40, and there are currently no prospective studies on how many opioid pills should be prescribed to patients discharged from the ED with common pain conditions in order to limit unused pills. Preliminary results from our group revealed that two-thirds of the total prescribed opioids were not consumed and remained available for misuse.

Objectives

The ultimate goal of this research program is to decrease opioid misuse by lowering the quantity of unused medications. The primary objective of this project is to determine the quantity of opioids consumed during the acute pain phase (2 weeks) by ED-discharged patients treated for an acute pain condition. The secondary objectives are to inventory the quantity of opioids prescribed and unused after ED visits, use of co-analgesics, pain intensity, health services revisits during the 2-week follow-up, and chronic pain prevalence at 3 months.

Methods

The investigators propose a multicentre prospective observational cohort study in 2,560 consecutive ED patients recruited from 6 Canadian hospitals. The study will include patients aged ≥18 years, treated for an acute pain condition present for less than 2 weeks (usual acute pain definition), and discharged from the ED with an opioid prescription. Pain at triage and at ED discharged, diagnosis, and complete pain medication prescription will be initially listed. Patients will complete a 14-day electronic diary using the REDCap web-based system to document their daily pain medication consumption, pain intensity, new opioid prescriptions, and health services revisits. Patients will also answer questionnaires at 2 weeks and 3 months for our various secondary objectives. To validate the patient self-report opioid consumption, a randomized subset of patients will come back to the emergency for a follow-up visit and a manual count of the remaining opioids. As mitigation strategies (validated in our pilot study), non-responders to the diary will be contacted by phone at 2 weeks to answered questions summing diary information, and paper versions will be available for patients without Internet access.

Sample size estimation

The sample size was calculated to obtain an accurate estimate of the mean quantity of 5 mg morphine pill equivalent that patients will consume during the first 2 weeks after ED visit for each pain condition (primary objective). Our preliminary study was used to determine the standard deviation of opioids consumed after discharge from ED (SD=16). To estimate the mean 5 mg morphine pill equivalent consumed for each of the five pain conditions (acute back pain, fracture, sprain/contusion, renal colic, and other) with a 95%CI margin of error of 1.5 pills (or ~10% of the SD) with a standard deviation of 16 pills, each diagnostic category requires 440 patients. With the 14% attrition rate observed during our pilot study at two weeks, a total of 2,560 patients will be recruited (512 patients - 72 lost to follow-up = 440 patients per pain condition). Sample size calculations were performed using PASS (Power Analysis \& Sample Size software, version 11.0: NCSS Statistical Software).

Feasibility

The investigators demonstrated the study feasibility in a successful pilot study with 627 patients at our academic ED. Additionally, our project brings together a committed, multidisciplinary research team, and all proposed study sites have collaborated previously on large multicentre studies. Finally, all instruments have been successfully tested, allowing rapid study implementation.

Impact

Our results will determine the quantity of opioids consumed during the acute pain phase (2 weeks) to ED-discharged patients treated for acute pain conditions. Our team members from relevant provincial and national stakeholders and patient associations, our strong evidence, and our extensive knowledge transfer strategy have the potential to impact physicians' opioid prescription practices. Consequently, fewer unused prescription opioids should lead to a substantial decrease in the currently high rate of opioid misuse.