Non-Opioid Option for Acute Traumatic Pain – Methoxyflurane (Penthrox™)
Analgesia / Sedation
- 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.
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.
Elimination: Urine (~60%, as metabolites); respiratory (~40%, unaltered or as carbon dioxide).
- 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?
We are highly confident that the true effect lies close to that of the estimate of the effect. There is a wide range of studies included in the analyses with no major limitations, there is little variation between studies, and the summary estimate has a narrow confidence interval.
We consider that the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. There are only a few studies and some have limitations but not major flaws, there are some variations between studies, or the confidence interval of the summary estimate is wide.
When the true effect may be substantially different from the estimate of the effect. The studies have major flaws, there is important variations between studies, of the confidence interval of the summary estimate is very wide.
- 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)
OTHER RELEVANT INFORMATION
Coffey, F., Dissmann, P., Mirza, K., & Lomax, M. (2016). Methoxyflurane analgesia in adult patients in the emergency department: a subgroup analysis of a randomized, double-blind, placebo-controlled study (STOP!). Advances in therapy, 33(11), 2012-2031.
Jephcott, C., Grummet, J., Nguyen, N., & Spruyt, O. (2018). A review of the safety and efficacy of inhaled methoxyflurane as an analgesic for outpatient procedures. British journal of anaesthesia, 120(5), 1040-1048.
Porter, K. M., Siddiqui, M. K., Sharma, I., Dickerson, S., & Eberhardt, A. (2018). Management of trauma pain in the emergency setting: low-dose methoxyflurane or nitrous oxide? A systematic review and indirect treatment comparison. Journal of pain research, 11, 11.
The purpose of this document is to provide health care professionals with key facts and recommendations for the diagnosis and treatment of patients in the emergency department. This summary was produced by the BC Emergency Medicine Network and uses the best available knowledge at the time of publication. However, healthcare professionals should continue to use their own judgment and take into consideration context, resources and other relevant factors. The BC Emergency Medicine Network is not liable for any damages, claims, liabilities, costs or obligations arising from the use of this document including loss or damages arising from any claims made by a third party. The BC Emergency Medicine Network also assumes no responsibility or liability for changes made to this document without its consent.
Last Updated Jul 18, 2019
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