Inhaled methoxyflurane: a promising alternative for treating trauma pain?

  • Ann Emerg Med
  • 14.10.2019

  • von Craig Hicks
  • Clinical Essentials
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Takeaway

  • Inhaled methoxyflurane (Penthrox) is an effective, nonnarcotic, rapid-acting alternative to standard analgesic treatments for trauma pain.

Why this matters

  • The FDA withdrew approval for methoxyflurane in 2005 because of nephrotoxicity and hepatotoxicity in humans.
  • The drug's manufacturer is seeking FDA reapproval based on new safety and dosing studies.

Study design

  • Patients with acute trauma-related pain (Numeric Rating Scale [NRS]-11 pain intensity, ≥4) were randomly assigned to either inhaled methoxyflurane (3-6 mL; n=156) or standard analgesic treatment (n=149; intravenous first-step analgesics, 70%; opioids, 9.4%).
  • Primary endpoints included pain intensity score change during the first 20 minutes of the treatment and time to first pain relief.
  • Funding: Mundipharma Pharmaceuticals S.L.

Key results

  • Mean NRS-11 decrease was greater for patients receiving methoxyflurane vs standard analgesics, with significant treatment differences of up to 20 minutes (mean NRS-11 score, 2.47 vs 1.39; treatment difference, 1.00; 95% CI, 0.84-1.32).
  • The methoxyflurane group had significantly less time to first pain relief vs the standard analgesic group (median, 3.17 vs 10.00 minutes).
  • Methoxyflurane had higher ratings for pain control and treatment comfort compared with standard analgesics: 77% of patients and 72% of clinicians vs 38% and 19%, respectively.

Limitations

  • Standard analgesic treatments varied widely, including oral and intravenous formulations and medication classes such as opioids, benzodiazepines, metamizole, and paracetamol.