Ellen Phiddian
Cosmos science journalist
Nitrous oxide, also known as laughing gas, is a popular recreational drug – and a team of Canadian researchers are concerned about its long-term toxicity.
Nitrous oxide is used legally as an anaesthetic, as well as being sold as a whipped cream propellant and for use as fuel in sports cars.
People also use the whipped cream canisters (referred to in Australia as ‘nangs’) to get a short high.
In the 2021 Global Drug Survey, 9.7% of the 32,000 respondents had used nitrous oxide in the last year.
A review in the Canadian Medical Association Journal has called for more attention to be paid to the negative effects of the drug.
“Although acute, heavy use of nitrous oxide can occasionally cause death by asphyxiation, isolated, short-term use rarely leads to serious complications,” write the authors.
“Regular inhalation, however, can have serious and even devastating neurologic consequences.”
Chronic use of nitrous oxide causes a vitamin B12 deficiency.
This deficiency then causes complications in the brain. According to the review, the three most common effects are spinal cord damage (myelopathy), nerve damage that affects strength and feeling (neuropathy), and new psychiatric conditions (from encephalopathy).
The most common treatment, for those admitted to hospital, is stopping nitrous oxide use and prescribing vitamin B12 supplements, sometimes with other medicines like methionine.
“Although the prognosis is variable, most (95%–97%) patients display at least partial improvement, but more than one-third of patients admitted to hospital have residual neurologic symptoms even after months of treatment,” write the researchers.
According to the review, scientists still don’t know what the optimal doses are for treating nitrous oxide toxicity. They also don’t know how to predict the risk of toxicity based on exposure. (The Australian Alcohol and Drug foundation reminds people: “there is no safe level of drug use” on its nitrous oxide information page.)
“The low cost of and ease of access to nitrous oxide make it a popular recreational drug, especially among younger people,” conclude the researchers.
“Clinicians should enquire about nitrous oxide use in patients with unexplained findings suggestive of vitamin B12 deficiency or other compatible neurologic symptoms.”