Methoxyflurane: A Review in Trauma Pain

Methoxyflurane (Penthrox^®) is a halogenated ether first used clinically as a volatile inhalational anaesthetic. It has been used as an analgesic in Australia and New Zealand for the past 30 years. In the UK and Europe, methoxyflurane has been approved for the emergency relief of moderate to severe trauma pain in conscious adult patients. Methoxyflurane is self-administered using a hand-held inhaler. This article reviews the pharmacological properties of methoxyflurane and its clinical efficacy and tolerability in these patients. In the phase III STOP! trial, methoxyflurane was effective and generally well tolerated for the management of acute pain due to minor trauma, with a rapid onset of analgesia. In a prospective study, methoxyflurane was more effective than intramuscular tramadol when administered for the treatment of acute musculoskeletal pain in the pre-hospital setting (i.e. by paramedics). Methoxyflurane had a more rapid onset of action than tramadol when administered for the treatment of pain related to ankle injuries in the emergency department. Although methoxyflurane is known to be potentially nephrotoxic at anaesthetic doses, the much lower doses used for pain relief were not associated with nephrotoxicity or an increased risk of renal disease. Inhaled methoxyflurane may offer advantages over other analgesics administered via the intravenous, intramuscular or intranasal routes in terms of its non-invasive self-administration, ease of use and/or rapid onset of action. As such, it is a useful additional treatment option for the management of trauma pain in the pre-hospital or emergency department setting.