#164 Double-blind randomised placebo-controlled study of paediatric acute trauma pain treatment with methoxyflurane

<h3>Background</h3> Methoxyflurane [MF; PENTHROX®] is a rapidly acting, self-administered non-narcotic analgesic. This study assessed efficacy of MF for treating acute pain in children attending emergency departments (EDs) following traumatic injury. <h3>Methods</h3> Phase III, randomised, double-blind, placebo [P] controlled study at 11 UK and Ireland EDs. Children aged 6 to &lt;18 years with pain scores of 60-80mm on a 100mm visual analogue scale (VAS) were randomised 1:1 to P (sodium chloride 0.9% 2x5mL) or MF (2x3mL) for up to 10 successive inhalations, with further intermittent inhalations as required. The primary endpoint was a pre-specified subgroup analysis of MF efficacy in the 9-&lt;18 year population. <h3>Results</h3> 4,513 screened, 249 randomised and 192 treated (of 220 planned, MF 92, P 100 overall; 159 in the age 9 to &lt;18 subgroup (MF 76; P 83)). The mean (standard deviation [SD]) age was 11.1 (2.5) years, 17% 6-8 years, 42% 9-&lt;12 years, 41% 12-&lt;18 years; male 56% and white 66%. In the subgroup, mean (SD) age was 11.8 (1.94) years and baseline pain was MF 71.2 (6.96) mm and P 70.4 (6.88) mm. At 15-min, the mean change from baseline in VAS was MF -20.0mm and P -13.2mm (-6.8mm difference [95% CI -12.5 to -1.2mm], p=0.018) in the subgroup; -7.0mm difference [95% CI -12.5 to -1.5mm], p=0.013 overall. Fewer participants in the MF arm required rescue medication (MF 9.8% vs. P 30.0%). Adverse events were more common in the MF arm (64%) versus P arm (55%). The most common related treatment emergent adverse event (TEAE) was dizziness (MF 40%, P 9%). 9 MF participants discontinued due to TEAE, and 1 in the P group. <h3>Conclusions</h3> In this placebo controlled pivotal trial, methoxyflurane was proven efficacious for the treatment of acute trauma related pain in children and adolescents, with a safety profile consistent with the adult population.