methoxyflurane: clinical use

Prescribing considerations

• Confirm that the patient is conscious, able to self-administer, and suitable for supervised inhaled analgesia.
• Review renal and hepatic history, previous anaesthetic reactions, current medicines, and recent methoxyflurane exposure.
• Use the activated-carbon chamber and instruct the patient to exhale through the inhaler to limit occupational exposure.
• It is unsuitable for repeated exacerbations of chronic pain or closely repeated trauma-pain episodes.

Contraindications and cautions

• Use as an anaesthetic agent
• Hypersensitivity to methoxyflurane, fluorinated anaesthetics, or an excipient
• Known or genetic susceptibility to malignant hyperthermia
• Personal or family history of severe reactions to inhaled anaesthetics
• Previous liver injury after methoxyflurane or halogenated hydrocarbon anaesthesia
• Clinically significant renal impairment
• Altered consciousness from any cause
• Clinically evident cardiovascular instability or respiratory depression

Monitoring

• Observe consciousness, respiration, and oxygenation during administration.
• Assess for excessive sedation, hypotension, and inadequate analgesia.
• Consider renal or hepatic assessment when clinically indicated, particularly after concerning symptoms or in patients with relevant risk factors.
• Minimise staff exposure by ensuring correct use of the activated-carbon chamber.

Clinical pharmacology

Methoxyflurane is highly lipophilic and is metabolised mainly by CYP2E1, CYP2B6, and CYP2A6. Metabolism produces fluoride and oxalate compounds that can damage the kidneys at excessive exposure; the parent compound is partly exhaled and metabolites are largely eliminated in urine.

Formulation and product differences

• The selected product is a clear, volatile inhalation liquid containing methoxyflurane and butylated hydroxytoluene as a stabiliser.
• It is administered only through the dedicated handheld inhaler with an activated-carbon chamber; it must not be used for general anaesthesia.