The Reincarnation of Methoxyflurane

Abstract

Methoxyflurane was an inhaled agent commonly used for general anesthesia in the 1960s, but its clinical role gradually decreased in the 1970s because of reports of dose-dependent nephrotoxicity. In 1999 its manufacturer, Abbott Laboratories, discontinued distribution of methoxyflurane in the United States and Canada. Outside of North America, however, methoxyflurane has been reborn as an inhaled analgesic used for pain relief in the prehospital setting and for minor surgical procedures. First used in Australia and New Zealand, and subsequently in over thirty-seven other countries, low concentrations of methoxyflurane are administered with a hand-held inhaler which provides conscious sedation, so that patients can self-assess their level of pain and control the amount of inhaled agent. The Penthrox inhaler, originally developed in Australia after several other hand-held vaporizers were tried, is currently being used worldwide as a portable and disposable self-administered agent delivery system. Methoxyflurane-induced nephrotoxicity continues to be a major concern, but with cautious administration of recommended doses methoxyflurane has been established as a remarkably safe analgesic agent with minimal side effects for patients in need of rapid and potent pain relief.