A review of the safety and efficacy of inhaled methoxyflurane as an analgesic for outpatient procedures

Abstract

Methoxyflurane delivered via a hand-held inhaler is a proven analgesic which has been used in Australasia for emergency relief of trauma associated pain since the 1970s. The agent is self-administered by the patient under the supervision of trained personnel. More than 5 million patients have received inhaled methoxyflurane without significant side effects. Methoxyflurane is also licensed in Australasia for the relief of pain in monitored conscious patients requiring analgesia for minor surgical procedures. Recent clinical studies undertaken in a variety of outpatient settings, including colonoscopy, prostate biopsy, dental procedures, bone marrow biopsy, and the management of burns dressings, indicate that inhaled methoxyflurane has significant analgesic activity, without producing deep sedation or respiratory depression. Return to full psychomotor activity is rapid. Thus, methoxyflurane may be a suitable and well-tolerated alternative to traditional i.v. sedative agents for outpatient medical and surgical procedures. There are direct advantages to the patient in terms of rapid recovery and an early return to normal activities, and significant benefits for outpatient departments in terms of cost saving and rate of throughput. Further randomised controlled trials comparing the efficacy, safety, and cost-effectiveness of inhaled methoxyflurane against traditional i.v. sedative techniques are currently in progress.

Comparison of inhalational methoxyflurane (Penthrox®) and intramuscular tramadol for prehospital analgesia

“…Fourth, the population was relatively naïve to methoxyflurane and this study would not pick up adverse effects that were related to repeated exposure, which although rare, have been reported in the published literature with the use of full anaesthetic doses. (20) Fifth, pain scores of patients after arrival at the emergency department were not available. Sixth, we did not collect information, such as pulse oximetry and possible desaturation.…”

Methoxyflurane (Penthrox®)—a case series of use in the prehospital setting

“…Despite a large volume of published literature supporting the efficacy and safety of methoxyflurane at analgesic doses (Blair et al, 2016;Jephcott et al, 2018), most studies have been observational and uncontrolled. However, two large randomised, controlled trials (RCTs) have compared methoxyflurane with placebo (Coffey et al, 2014) and with intramuscular (IM) tramadol (100 mg) (Lim et al, 2016).…”

“…As with all anaesthetics, the precise mechanism of action is unclear. Methoxyflurane is unique in this anaesthetic family in having well-documented analgesic properties at low doses (Blair et al, 2016;Jephcott et al, 2018).…”

Penthrox: a breath of PHEC air for the military?

“…However, within a few years concerns were raised about the nephrotoxicity of this agent. The mechanisms of the renal tubular dysfunction were never established but it fell from favour and its use declined 3 4. Despite this, in the 1970s the Australian emergency services started using a reduced dose of methoxyflurane as an inhaled analgesic for trauma pain relief.…”