Methoxyflurane

How it works

It is a volatile fluorinated agent that, at the low analgesic concentrations self-administered by inhalation, produces analgesia through actions on the central nervous system; the precise mechanism is not fully established.

Prescribing in practice

• Total cumulative exposure must be limited because of the risk of dose-related nephrotoxicity and hepatotoxicity, and it is contraindicated in clinically significant renal impairment and in personal or family history of malignant hyperthermia.
• It is self-administered by the patient through the inhaler under supervision, allowing them to titrate to effect; repeated use on consecutive days should be avoided.
• Avoid concomitant use with agents that may worsen renal or hepatic toxicity; consult the SPC and follow exposure limits.

Monitoring

Monitor pain relief, conscious level, and ensure cumulative exposure limits are observed, with caution regarding renal and hepatic function.

Counselling the patient

• Breathe through the inhaler to control your pain; take slow breaths and use more if you need it.
• You may feel lightheaded or drowsy, which passes after you stop using it.
• This is for short-term pain relief and should not be used repeatedly over consecutive days.

Evidence & guidelines

Methoxyflurane is licensed for emergency relief of moderate to severe trauma pain in conscious adults, supported by trial evidence such as the STOP! study and used within UK emergency and prehospital settings.