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Intended for UK Healthcare Professionals

Methoxyflurane – The Facts

  • Methoxyflurane belongs to the family of volatile fluorinated hydrocarbons. Other members of this family are anaesthetic drugs, such as sevoflurane and desflurane.
  • Methoxyflurane was originally used as an anaesthetic drug, however, it was found to have analgesic effects at sub-anaesthetic doses.1
  • It has been in use as an analgesic in Australia since 1975 and has continued to be used in Australia and New Zealand as an inhaled analgesic, in the form of PENTHROX, for over 30 years.3
  • Methoxyflurane can cause dose-related nephrotoxicity;1 a clinical study identified that nephrotoxicity occurred at doses in excess of 2.5 MAC-hours*; these doses were reached when methoxyflurane was used for anaesthesia.3
  • As a result of this clinical study a safe upper limit for methoxyflurane exposure was determined to be 2 MAC-hours – doses below 2 MAC-hours have not been associated with nephrotoxicity.3
  • Methoxyflurane administered via the PENTHROX inhaler (3 mL dose) equates to approximately 0.3 MAC-hours.3
  • Patients are limited to 2 doses (2 x 3 mL) PENTHROX in a single day to ensure exposure to methoxyflurane is kept well below the safe upper limit.1
  • Serious dose-related nephrotoxicity has only been associated with methoxyflurane when used in large doses over prolonged periods during general anaesthesia.1
  • PENTHROX was approved by the regulatory authorities for use in the UK and Ireland in late 2015.


*MAC-hours: minimum alveolar concentration (MAC) multiplied by duration of administration (hours)

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