Methoxyflurane

Inhaled methoxyflurane can be used in a wide range of settings (eg before hospital arrival, in emergency departments, in outpatient clinics) because of its ease of administration. It is most commonly used for acute pain associated with trauma but can also be used for procedure-related pain (eg reduction of dislocation, wound repair, bone marrow biopsy).

Methoxyflurane is self-administered. Effective use of the device requires patients to be conscious and cooperative (eg it cannot be reliably used by children younger than 5 years). Use should be supervised by a trained healthcare practitioner, and limited to settings where resuscitation facilities are available. Furthermore, it should be used in a well-ventilated environment to minimise nonpatient exposure—the portable inhaler minimises, but does not eliminate, nonpatient exposure.

The onset of analgesic effect is rapid (occurring after 5 to 8 inhalations) and persists for several minutes after use—used continuously, a 3 mL cartridge provides approximately 20 to 30 minutes of analgesia.

Except in children younger than 5 years, methoxyflurane is unlikely to cause more than transient conscious sedation because it requires patient coordination to maintain effect. However, concomitant use of opioids or other sedatives increases the risk of deep sedation. In children younger than 5 years, deep sedation and apnoea can occur, so methoxyflurane should be avoided.

Serious adverse effects with self-administered methoxyflurane are rare but minor adverse effects (eg dizziness, headache) are common. Nephrotoxicity can occur with higher doses and prolonged use, so doses should not exceed a volume of 6 mL in a 24-hour period or 15 mL in a week. Methoxyflurane is not appropriate for repeat procedures in children because there is a lack of safety data to support this practice.