Background
Low-dose methoxyflurane administered via a handheld inhaler (Penthrox®) has been used for over 40 years in Australia and New Zealand for short-term pain relief in emergency medicine. The STOP! study[1,2] investigated the efficacy and safety of methoxyflurane analgesia for the treatment of acute pain in adult and adolescent patients presenting to the ED with minor trauma and moderate to severe pain (score of 4-7 on the Numeric Rating Scale [NRS]). We present a post hoc analysis of Global Medication Performance (GMP) and adverse events (AEs) in a subgroup of patients with severe pain (NRS=7) at baseline.

Material and methods
At triage, patients (N=300) were randomised 1:1 to receive methoxyflurane (up to 6mL) or placebo (normal saline), self-administered as required via a Penthrox® inhaler. Rescue medication (paracetamol/opioids) was available immediately upon request. The patient, treating physician and research nurse each rated GMP at ED discharge as “Poor”, “Fair”, “Good”, “Very Good”, or “Excellent”. AEs were recorded from enrolment until discharge, and at safety follow up (Day 14±2).

Results
The severe pain subgroup included 62 methoxyflurane-treated patients and 71 placebo-treated patients. The most common injury types were “other” (49%, mostly sprains, soft tissue injury and muscular pain), contusions (23%) and fractures (19%). GMP ratings by the patient, physician and nurse at ED discharge were all significantly better in the methoxyflurane group compared with the placebo group (p<0.0001 for patient and nurse ratings and p=0.0004 for physician rating). 81% of patients, 85% of treating physicians and 77% of research nurses in rated methoxyflurane treatment as “Good”, “Very good” or “Excellent”, compared with 41%, 51% and 35% in the placebo group. AEs were reported by 31 patients (50%) in the methoxyflurane group and 30 patients (42%) in the placebo group and were mainly mild and transient in nature. AEs reported by ≥5% of patients were dizziness (29%), headache (15%) and somnolence (6%) for methoxyflurane and headache (17%), dizziness (7%), nausea (7%), vomiting (6%) and hypotension (6%) for placebo. 

Conclusion
Patient and treating physician/nurse satisfaction with low-dose methoxyflurane treatment administered via the Penthrox® inhaler was high (≥77%) for this subgroup of patients presenting to the ED with severe trauma pain (NRS=7 at baseline).

References
1.	Coffey F et al. Emerg Med J;31:613-8, 2014.
2.	Coffey F et al. Adv Ther;33:2012-31, 2016.

Acknowledgements
The study was funded by Medical Developments International (MDI) Limited. Karen Mower (Scientific Editorial) provided medical writing services on behalf of Mundipharma Research Limited. Frank Coffey was paid travel and subsistence expenses by MDI for one investigator’s meeting. There were no other competing interests.

® PENTHROX is a registered trademark of MDI Limited.



09 / Global medication performance and safety of methoxyflurane analgesia in patients with severe acute trauma pain treated in the emergency department: a sub-analysis of a randomised, double-blind, placebo-controlled UK study