A randomised, double-blind, cross-over study to assess the analgesic effect of methoxyflurane at moderate high altitudes in a wilderness field setting.

Phase IV, randomised, double-blind, cross-over clinical trial to evaluate the analgesic effect of methoxyflurane at moderate high altitudes in a wilderness field setting, in 24 healthy volunteers

Primary outcome: To assess the analgesic efficacy of inhaled methoxyflurane at moderate high altitudes in a wilderness setting.

Secondary outcomes: To assess the comparative safety and adverse events with inhaled methoxyflurane at moderate high altitudes in a wilderness setting.

Inclusion Criteria:

1. Male or female between 18 and 65 years of age (inclusive).
2. Able to provide informed consent and comply with study-related procedures

Exclusion Criteria:

1. History of diabetes
2. Renal or hepatic disease or impairment (defined as a value exceeding the maximum reference range)
3. Chronic or nociplastic pain
4. Chronic fatigue syndrome
5. Chronic/regular use of analgesic medications
6. Personal or familial history of malignant hyperthermia
7. Personal or familial history of anaesthesia-induced rhabdomyolysis
8. Personal history of anaesthesia volatile-induced hepatitis or drug induced liver injury
9. Recent volatile anaesthesia (within 6 months)
10. History of significant altitude-related illness
11. Significant underlying medical condition which precludes gentle exercise at moderate high altitude (<2500 m ASL) as determined by the investigators
12. Hypersensitivity to Penthrox/Penthrop®, methoxyflurane or any fluorinated anaesthetic.
13. Concurrent treatment with CYP 2A6 or CYP 2E1 enzyme inducers (such as: phenobarbital, rifampicin, alcohol or isoniazid)
14. Pregnancy

double-blind