Nitrous oxide

nitrous oxide

Overview

Nitrous oxide belongs to Dissociatives.

Key safety note: The commonest acute cause of death with nitrous oxide is not the gas itself but oxygen deprivation: inhaling pure N₂O, especially from a mask, a bag over the head, or in a sealed car or small room, displaces oxygen and can cause hypoxia, loss of consciousness and death by asphyxia.[3][4]
Effects
Subjective effects vary. What a substance feels like depends on dose, individual physiology, mindset, and setting. The points below describe commonly reported effects, not guaranteed, uniform, or desirable outcomes.
  • A rapid, short-lived rush of euphoria, giddiness and uncontrollable laughter, with dissociation, dreamy detachment and a sense of floating.
  • Distorted or echoing sound and vision, tingling, dizziness and heaviness of the body.
  • Effects fade within about a minute. Repeated redosing brings headache, disorientation and, with heavy use, the numbness and unsteadiness of B12-related nerve damage.
Dosing & duration
Harm-reduction note: These are commonly cited reference ranges, not a recommendation or a “safe” dose. Potency, purity, body chemistry, tolerance, and drug combinations vary widely. Start low, go slow, wait for full effects before redosing, and never assume an unknown product matches these figures. Missing data is not evidence of safety.

Inhaled: medically as a metered gas mixed with oxygen. Recreationally from a balloon. There is no milligram 'dose'.. Not a recommendation. Nitrous oxide is inhaled, not dosed in milligrams, and the danger scales with how it is taken. NEVER inhale from a mask, tube or bag, or in a closed space (car, tent, sealed room). This displaces oxygen and causes asphyxia. Never inhale directly from a pressurised tank or charger (frostbite and lung injury). If used: sit down, use a single balloon at a time with normal air between breaths, keep sessions short and infrequent, and take vitamin B12: frequent heavy use is what causes the (sometimes permanent) nerve and spinal-cord damage.

Dose ranges

Medical (Entonox)

50% N₂O / 50% O₂, self-administered and titrated

Recreational

A balloon filled from a charger, never a mask, and never straight from the tank

Duration

onset

Seconds

total

≈1–2 min

after effects

Brief dizziness/headache. Nerve damage with heavy repeated use

Chemical & Physical Properties
FormulaN2O
Molar mass44.01 g/mol
StateGas
Melting point-90.81 °C
Boiling point-88.46 °C
Density1.266 g/cm³ at -89 °C (USCG, 1999)
Vapor pressure51.3 atm (NIOSH, 2024)
pKaNot reported
LogP0.36
Solubility0.1 % at 25 °C (NIOSH, 2024), Slightly soluble in water, At 20 °C and 2 atm one liter of the gas dissolves in 1.5 liters of water
Refractive index1.000516 at 0 °C (D line, 0.5893 µm, 1 atm)
Identifiers & Synonyms
CAS10024-97-2
CAS (enantiomer)
PubChem CID948
InChIKeyGQPLMRYTRLFLPF-UHFFFAOYSA-N
InChIInChI=1S/N2O/c1-2-3
SMILES[N-]=[N+]=O

Synonyms

  • Laughing gas
  • Dinitrogen monoxide
  • Nitrous
  • N2O
  • Whippits (misuse)
  • Nos
  • Nangs
  • Whippits
Pharmacodynamics & Biochemistry

Nitrous oxide (N₂O, 'laughing gas') is an inhaled gas with anaesthetic, analgesic and dissociative/euphoriant effects. Its main psychoactive and anaesthetic action is non-competitive antagonism of the NMDA glutamate receptor, the same channel-blocking mechanism as ketamine, which produces the dissociation, analgesia and anaesthesia. It also releases endogenous opioid peptides (contributing to pain relief) and modulates GABA-A, glycine and two-pore (TREK) potassium channels. The subjective effect comes on within seconds of inhalation and fades within a minute or two, because the gas enters and leaves the brain extremely quickly. It is essentially not metabolised and is exhaled unchanged. This ultra-short action is why recreational users redose repeatedly from balloons. Uniquely among common drugs, nitrous oxide is chemically reactive with vitamin B12: it irreversibly oxidises the cobalt atom of cobalamin and thereby inactivates the B12-dependent enzyme methionine synthase. Occasional use is inconsequential, but heavy or frequent use functionally depletes B12 and can cause subacute combined degeneration of the spinal cord and a peripheral neuropathy: numbness, tingling, weakness and unsteadiness that can become permanent.

Biological targets

  • NMDA
Pharmacokinetics
BioavailabilityInhalational, rapid alveolar uptake
TmaxSeconds to minutes
Half-lifeVery short, cleared within minutes of cessation
VdNot reported
Protein bindingNot reported
MetabolismEssentially not metabolized
ExcretionEliminated unchanged via the lungs
Toxicology & Safety
Harm-reduction note: Toxicity and risk depend on dose, route, purity, combinations, setting, and individual health factors. Missing harms should never be interpreted as evidence of safety.

Not reported

The commonest acute cause of death with nitrous oxide is not the gas itself but oxygen deprivation: inhaling pure N₂O, especially from a mask, a bag over the head, or in a sealed car or small room, displaces oxygen and can cause hypoxia, loss of consciousness and death by asphyxia. Direct inhalation straight from a pressurised cartridge or tank can also cause cold (frostbite) injury to the lips, airway and lungs, and rapid pressure changes can rarely rupture lung tissue. The distinctive longer-term harm is neurological: because N₂O inactivates vitamin B12, heavy or frequent use causes B12-functional deficiency with subacute combined degeneration of the spinal cord and peripheral neuropathy: tingling, numbness, weakness and difficulty walking that may not fully recover. Falls and injuries occur from the sudden loss of coordination and consciousness, and dependence with very heavy daily use is increasingly reported. Harm reduction: never use a mask or an enclosed space, sit down, use one balloon (never straight from the tank) at a time, keep use occasional, and maintain vitamin-B12 intake.[3][4]

Legal Status
Legal note: Legal status can change over time and may vary by country, region, formulation, analogue status, prescription context, and enforcement practice. Always confirm with current official sources before relying on this section.
Interactions & Contraindications

Drug interactions

Alcohol, Opioids, General anaesthetics and other sedatives Additive sedation and impairment, and a greater hypoxia risk.[4]
Antifolate drugs (methotrexate) or low vitamin B12 status Nitrous oxide inactivates vitamin B12 (methionine synthase), so low B12 status or antifolate drugs such as methotrexate worsen the neuro-toxicity through folate and methionine interference.[3]

Contraindications

Vitamin B12 deficiency (dietary or functional) functional or dietary.[3]
Trapped gas: pneumothorax, bowel obstruction, air embolism, middle-ear or sinus block, or recent intraocular gas[2]
Settings where impairment or dissociation risks injury (driving, water, heights) an enclosed or oxygen-poor space, or breathing it from a mask or bag (asphyxia risk).[4]
Pregnancy or breastfeeding first trimester (relative).[2]
Usage & Context
  • A long-established medical gas: an adjunct in general anaesthesia, a sedative in dentistry, and, as a 50:50 mix with oxygen (Entonox/'gas and air'), an analgesic in labour and emergency care.
  • Widely used recreationally for its brief euphoria and giddiness, inhaled from balloons filled from small 'whippit'/'nang' cream chargers or, increasingly, large catering tanks.
  • Also an industrial and culinary product (whipped-cream propellant, rocket/engine oxidiser) and a significant greenhouse gas.
Sources & Evidence

Further Information