Nitrous Oxide / Oxygen

What it is and how it works

A premixed equimolar mixture of nitrous oxide and oxygen that provides rapid-onset, rapidly reversible analgesia through the analgesic effects of nitrous oxide, while the high oxygen content prevents hypoxia.

Indications

Short-term analgesia for painful procedures and conditions, including labour, emergency care, dressing changes, minor procedures and dental treatment.

Dosage and administration (summary)

Self-administered by inhalation through a demand valve with mask or mouthpiece; the patient should hold the mask so that administration stops if drowsiness occurs. Duration is limited by the risks of prolonged exposure.

Contraindications

Pneumothorax, air embolism, decompression sickness, bowel distension or obstruction, recent intraocular gas injection, head injury with impaired consciousness, and vitamin B12 deficiency.

Warnings and precautions

Prolonged or frequent use may cause vitamin B12 inactivation with megaloblastic anaemia and neuropathy. Sedation enhances other CNS depressants; patients should not drive until fully recovered. Ensure adequate ventilation and scavenging to reduce staff exposure.

Pregnancy

Widely used for analgesia in labour; prolonged exposure in early pregnancy should be avoided.

Storage and supply

Store cylinders above about −6 °C, as the gases may separate at low temperatures; if exposed to cold, cylinders must be warmed and mixed before use as instructed by the supplier.

Source: reference summary prepared from the EU SmPC/EPAR, BNF and WHO Model Formulary. The approved product information in Iran governs.