Table 1 Inclusion and exclusion criteria

 > 18 years of age

Life-threatening or limb-threatening condition requiring immediate management

Acute moderate to severe pain (both medical and traumatic etiology) defined by self-reporting pain ≥ 4 on numeric rating scale

Pregnancy or breastfeeding

Capable of giving informed consent

Know allergies, hypersensitivity, or serious side effects to opioids or methoxyflurane or other excipients

Normal physiology

Head injury or medical conditions with neurological impairment (Glasgow coma scale < 14)

Previous malignant hyperthermia or persons with suspect genetic predisposition for malignant hyperthermia

Massive facial trauma, visible nasal blockage, or on-going nose bleeding

History of severe liver disease with jaundice and scleral icterus

Dialysis or history of severe renal disease (known chronic kidney failure stage 4 or 5)

Monoaminoxidase inhibitors last 14 days (pharmacological treatment of depression, Morbus Parkinson or narcolepsy)

Myasthenia gravis

Use of investigational medicinal product analgesics 12 h prior to inclusion

Any condition that in the view of the study worker would suggest that the patient is unable to comply with study protocol and procedures