Rationale. Musculoskeletal trauma (MSK-T) in children is very common and almost universally painful. Standards for children's pain management of MSK-T in the Emergency Department (ED) vary greatly between Canadian hospitals and, overall, pain is very poorly treated. This inadequate pain treatment can have significant acute and chronic negative effects. Previous studies have determined that monotherapy with ibuprofen, the most commonly prescribed oral analgesic in the ED, is likely providing inadequate pain management for children. In response to this problem, clinicians have turned back to classic oral opioids (eg morphine) and are experimenting with combination therapies. To date, few studies have focused on the efficacy of a combination of a non-steroidal anti-inflammatory drug (NSAID) (eg ibuprofen) and an opioid (eg morphine). Such a combination of analgesics is known to potentiate pain relief by blocking it at the level of both the peripheral and the central nervous system. By combining two drugs with different mechanisms of action, we may be able to provide additive analgesic effects. To our knowledge, no studies have ever studied the efficacy and safety of this combination of medication for MSK-T in pediatric EDs. Primary Hypothesis: For children with a MSK-T in the ED, the addition of morphine to ibuprofen is safe and provides better pain relief than either of the two drugs alone. Primary Research Question: For children with a MSK-T in the ED, is a combination of oral morphine (0.2 mg/kg) and oral ibuprofen (10 mg/kg) more efficacious than either of the two drugs, alone, in decreasing pain scores to \<30 mm, 60 minutes after administration?

Methods. Design: This study is a double-blind, placebo-controlled, two center, three-arm, randomized clinical trial (RCT). Patients will be randomized to receive either: (a) ibuprofen (10mg/kg) + placebo or (b) morphine (0.2 mg/kg) + placebo or (c) morphine (0.2mg/kg) + ibuprofen (10mg/kg). Setting: Stollery Children's Hospital (Edmonton, AB) and CHU Ste.Justine's pediatric hospital (Montreal, PQ). Inclusion criteria: We will include children: (a) between the ages of 8 and 17 years; (b) visiting the ED with an injured upper or lower limb that is neither obviously deformed, nor neurovascularly compromised, (c) with a self-reported pain score \>30 mm on a 0 to100mm Visual Analogue Scale (VAS), where 0 mm corresponds to no pain and 100 mm to the worst pain the child has experienced, and (d) who understand French or English. Sample Size: Based on previous studies, we expect that between 25-52% (Clark et al., 2007, Le May et al., 2013) of children will achieve a VAS \< 30 mm at 60 minutes in the ibuprofen arm. We have conservatively set the proportion of children with VAS \< 30 mm at 60 min to 50%. A sample size of 500 will be then necessary to provide at least 80% power to detect a 20% absolute difference in proportion using a two-tailed with an alpha level of 5%. In order to ensure an overall alpha level of 5%, a Bonferroni correction has been applied in order to take into account the 3 pairwise comparisons that will be performed. Primary Outcome and Measurement: The primary outcome measure will be pain intensity score under 30 mm at 60-minutes after medication administration, using the VAS). Primary Safety Outcomes: We will also assess clinical measures of safety by monitoring oxygen saturation at 30 minutes intervals, up until 120 minutes. Level of sedation/alertness, as well as the respiratory rate, of each child will be monitored at set time points in the study, up until 120 minutes. Participating children will be followed up (via phone call) at 24 hours, to record any latent side effects or adverse events. Further, acceptability of the intervention will be assessed.

Relevance: Our proposed work will be the first RCT to investigate if there is some additive effect of a bi-therapy of pain with ibuprofen and morphine. In summary, currently available research supports ibuprofen as the monotherapy agent of choice. However, given concerns regarding its ability to provide adequate relief on its own, smaller studies looked at morphine as a possible alternative combined to ibuprofen. Very few studies of analgesic combinations exist, and as such, we have yet to identify the optimal ED pain management strategy for children with MSK-T. A larger trial with careful control over principal sources of bias and a rigorous approach to safety data collection will provide clinicians with strong evidence regarding efficacy and safety on new therapeutic strategies for pain management related to MSK-T in the pediatric EDs.