Penthrox (methoxyflurane) is suitable for use in conscious adults, who can self-administer the drug in an emergency under the supervision of a healthcare professional.
Methoxyflurane is a halogenated hydrocarbon anaesthetic that provides analgesia when inhaled at low concentrations. It should not be used in patients with a history of hepatotoxic reactions to halogenated hydrocarbon anaesthetics or a family history of malignant hyperthermia.
In a randomised, double-blind, placebo-controlled study in 300 patients presenting to emergency departments with minor trauma, methoxyflurane reduced pain intensity significantly more than placebo (p<0.0001) when assessed at 5, 10, 15 and 20 minutes after inhalation. The greatest estimated treatment effect (adjusted change from baseline -18.5 mm) was seen at 15 minutes after the start of treatment.