Entonox

Entonox, referred to colloquially as gas and air, is an anaesthetic and analgesic used to ease pain during labour, trauma and minor surgical procedures. Entonox is the trade name for a mixture of fifty percent nitrous oxide (N₂O or laughing gas) and fifty percent oxygen so a more appropriate name would be gas and oxygen. Entonox is administered by inhalation from a cylinder at a pressure of 137 bar (in the UK) or from a pipeline supply. Its analgesic effect is strong and characterised by rapid onset and offset (i.e. it is very fast-acting and wears off very quickly).

Entonox is not just any 50:50 mixture of oxygen and nitrous oxide, it is a premixed 50:50 composition that is self administered i.e. there is no requirement for an anaesthetist to be present to (amongst other things) control the mix of nitrous oxide and oxygen. (The 50% oxygen in Entonox ensures the user is always inhaling sufficient oxygen to prevent asphyixiation, thereby rendering it safe for self-administration.)

Entonox is produced by the BOC Group who also own the trademark.

NB: when using Entonox it is important to note that the pain relief reaches a maximum after about 30 seconds of continuous inhalation and it should be used accordingly. During childbirth, for example, it is important to start breathing it about 30 seconds before the contraction peaks.

External links

• BabyCentre entry on Entonox
• Detailed medical analysis of the drug