Medications
Nitrous Oxide
Inhalational analgesic for self-administered relief of moderate to severe pain
Last updated: 2026-04-12Original source from BCEHS
Indications
Authorized
Self-administered relief from moderate to severe pain
- Includes pain caused by extremity injuries, burns, or other injuries or clinical conditions not including inhalation injuries
Contraindications
- Traumatic or spontaneous pneumothorax
- Air embolism or decompression sickness following a recent SCUBA dive
- Bullous emphysema
- Gross abdominal distension
- Altered mental status or an inability to comply with instructions
- Inhalation injury (i.e., smoke or chemicals)
- Nitroglycerin use within five minutes prior to administration of nitrous oxide
Mnemonic: CDCPAIN
- Ability to Comply
- Decompression sickness
- Altered level of Consciousness
- Pneumothorax
- Air embolism
- Inhalation injury
- Nitroglycerin use within five minutes
Adult Dosages
Authorized
Relief from moderate to severe pain
- Self-administered to effect
Pediatric Considerations
Authorized
Relief from moderate to severe pain
- Self-administered to effect
Adverse Effects
- Lightheadedness, dizziness, numbness in lips, sedation, drowsiness, disorientation
- Nausea and/or vomiting
Additional Information
Mechanism of Action
As used in BCEHS, nitrous oxide is supplied as a 50/50 mixture with oxygen and is known as Entonox. Nitrous oxide is a sweet-smelling, colourless gas that is a potent analgesic and a weak anesthetic whose specific mechanism of action is not well understood. It is believed that endorphin release is likely involved in the analgesic effects of nitrous oxide.
Pharmacokinetics
| Route | Onset | Peak | Duration |
|---|---|---|---|
| Inhaled | Less than one minute following 4-5 deep breaths | Immediate | Requires continuous use |
Warnings and Precautions
- Nitrous oxide's blood/gas partition coefficent at body temperature is significantly higher than that of nitrogen's. It will therefore expand into internal gas spaces in the body, and must not be used in cases where additional gas loading would be dangerous (e.g., decompression sickness or air embolisms, abdominal distension, pneumothorax); this phenomenon accounts for the majority of nitrous oxide's contraindications.
- Nitrous oxide is excreted unaltered in the patient's breath. Administration must take place in a well-ventilated area to prevent others from inhaling the gas.
- Do not use nitrous oxide in confined spaces that cannot be adequately ventilated. When using nitrous oxide inside an ambulance, ensure exhaust fans are running or windows are open to provide for sufficient ventilation of the patient compartment.
- Do not use nitrous oxide aboard aircraft due to the risk of flight crew exposure.
- Nitrous oxide must be used with caution in patients who are hypotensive or in shock, have ingested or are suffering from the effects of depressant drugs, have a history of chronic obstructive pulmonary disease, or have suffered facial injuries.
Drug Interactions
The depressant effects of nitrous oxide can be potentiated by the presence of other CNS depressants such as alcohol, sedatives, antihistamines, or psychotropic medications.