Nitrous oxide (medication)

Nitrous oxide
Entonox CD cylinder and giving set
Combination of
Nitrous oxideAnalgesic gas (usually 50%)
OxygenMedical gas (usually 50%)
Clinical data
Trade namesEntonox, Nitronox, others
Routes of
administration
Inhalation
Drug classNMDA receptor antagonist; Dissociative hallucinogen; Analgesic; General anesthetic
ATC code
Legal status
Legal status
  • 50/50 mix of nitrous oxide and oxygen: ℞ (prescription only)
Pharmacokinetic data
MetabolismNot metabolized
MetabolitesNone
Onset of action30 seconds
Duration of action1 minute
ExcretionExhaled
Identifiers
CAS Number
PubChem CID
DrugBank
ChemSpider
UNII
ChEBI
ChEMBL
Chemical and physical data
FormulaN2O
Molar mass44.013 g·mol−1
3D model (JSmol)
  • Nitrous oxide: [N-]=[N+]=O
  • Nitrous oxide: InChI=1S/N2O/c1-2-3
  • Key:GQPLMRYTRLFLPF-UHFFFAOYSA-N

Nitrous oxide, as medical gas supply, is an inhaled gas used as pain medication, and is typically administered with 50% oxygen mix. It is often used together with other medications for anesthesia. Common uses include during childbirth, following trauma, and as part of end-of-life care. Onset of effect is typically within half a minute, and the effect lasts for about a minute.

Nitrous oxide was discovered between 1772 and 1793 and used for anesthesia in 1844. It is on the World Health Organization's List of Essential Medicines. It often comes as a 50/50 mixture with oxygen. Devices with a demand valve are available for self-administration. The setup and maintenance is relatively inexpensive for developing countries.

There are few side effects, other than vomiting, with short-term use. With long-term use anemia or numbness may occur. It should always be given with at least 21% oxygen. It is not recommended in people with a bowel obstruction or pneumothorax. Use in the early part of pregnancy is not recommended. It is possible to continue breastfeeding following use.