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    Non-Opioid Option for Acute Traumatic Pain – Methoxyflurane (Penthrox™)

    Analgesia / Sedation

    Last Reviewed on Jul 18, 2019
    Read Disclaimer


    • Methoxyflurane is a ‘new-to-Canada’, (May 2018, Health Canada approval) self-administered, inhalational analgesic that may contribute to quicker access to pain control for patients, support for brief painful procedures, and during patient transports in the out-of-hospital setting.
    • The handheld delivery system may permit less staff time and monitoring.
    • Further experience in the Canadian prehospital and in-hospital environments is required to determine if and where methoxyflurane may best fit in our practices. In 2018-2019, BC Emergency Health Services is trialing methoxyflurane at select ambulance stations in British Columbia. Therefore, BC Emergency physicians will receive patients who have been inhaling this medication.
    • A cost-analysis that compares personnel, ancillary equipment and medication between available modalities would be of value.
    • No longer used as a general anesthetic due to acute kidney failure with prolonged use.

    Recommended Treatment


    Moderate to severe pain associated with trauma in conscious adults or for performing brief interventional medical procedures.


    Dosage: Initial dose: 3 mL, may repeat another 3 mL after 20 minutes if needed; maximum dose: 6 mL/day.

    • Do not use on consecutive days if two doses were given (6 ml) on day 1, which wouldn’t be our common approach.
    • Consecutive days at 3 mL would be fine (example, supporting daily burn dressing change up to 5 days; then we hit the 15 ml weekly max).
    • Use lowest effective dosage to provide analgesia.
    • A treatment course should be limited to a total dose of 15 mL/week (no more than 6 mL/48 hours).
    • Treatment courses should not be repeated at an interval of less than 3 months.

    Route of Administration:  Self-administration as needed under direct supervision.

    Onset: Rapid (<5 minutes; 6-8 breaths).

    Duration of action: 25 to 30 minutes (continuous inhalation) or ~60 minutes (intermittent inhalation).

    Distribution: Highly lipophilic.

    Metabolism: Hepatic.

    Elimination: Urine (~60%, as metabolites); respiratory (~40%, unaltered or as carbon dioxide).

    Side Effects:

    • Major: Dizziness, headache.
    • Minor: Drowsiness, nausea, euphoria, anxiety, flushed skin, blood pressure changes, cough, dry mouth.

    Criteria For Close Observation And/or Consult

    Dependent upon the patient’s clinical presentation.

    Quality Of Evidence?


    • Self-administered inhaled methoxyflurane provided greater pain relief than placebo for patients with minor to moderate trauma and moderate pain in the emergency department. (HIGH QUALITY)
    • Inhaled methoxyflurane appeared to be safe and well tolerated. (HIGH QUALITY)
    • Methoxyflurane is less effective for pain relief in pre-hospital setting when compared to intravenous morphine or intranasal fentanyl. (MODERATE QUALITY)
    • A systematic review and indirect treatment comparison of methoxyflurane and nitrous oxide showed both agents provided well-tolerated rapid pain relief to trauma patients with no significant differences between them. (MODERATE QUALITY)

    Related Information


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    Penthrox Device Preparation

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