Pharmacological pain relief in labour

What it is

Entonox analgesia is an inhalational analgesia mix of 50% oxygen and 50% nitrous oxide. It is administered via an Entomix apparatus, through specially designed disposable tubing with an expiratory valve attached and a face mask or mouth piece for the patient to use for inhalation. It is self administered by the woman in labour, so she controls its use, and it is safe to use in conjunction with other methods of pain relief.

It works quickly, usually within 3 to 4 contractions, and wears off quickly when administration stops. It is useful as an aid to enhance coping strategies over a difficult patch, or whilst waiting for other forms of pain relief to take effect. Its use over more than 6 hours is not recommended.