Diagnosis and management of toxicity linked to recreational nitrous oxide use: Key points

Canada: Nitrous oxide has become a popular recreational drug owing to its low cost and ease of access, particularly among younger people. A recent review, published in CMAJ (Canadian Medical Association Journal), suggests that it can cause functional vitamin B12 deficiency and is an easily overlooked cause of neurologic abnormalities, typically, peripheral neuropathy, myelopathy or encephalopathy.

Salient features key pointsof Nitrous oxide toxicity are -

1.Recreational use of nitrous oxide is a growing problem in many jurisdictions, including Canada.

2. Although isolated, short-term use rarely leads to serious complications, chronic use can cause neurotoxicity that is often not fully reversible; cervical myelopathy, peripheral neuropathy and encephalopathy have been described.

3.The pathophysiology of nitrous oxide toxicity results from functional vitamin B12 deficiency.

4. Elevated homocysteine and methylmalonic acid are potential biochemical markers for the diagnosis, and magnetic resonance imaging and nerve conduction studies can help further define the presentation.

5. Cessation of nitrous oxide is the mainstay of treatment; supplementation with vitamin B12 and methionine are recommended.

"Clinicians should enquire about nitrous oxide use in patients with unexplained findings suggestive of vitamin B12 deficiency or other compatible neurologic symptoms," the researchers wrote in their research which aimed to help clinicians recognize signs of nitrous oxide toxicity.

Cessation of nitrous oxide is the mainstay of treatment; the researchers recommend supplementation with vitamin B12 and methionine.

Also known as “laughing gas,” nitrous oxide is an anaesthetic sometimes used in pediatric and dental procedures. Inexpensive and easily obtainable online, it is increasingly used for a quick high. In the 2021 Global Drug Survey, 10% of all respondents, and 15% of Canadian respondents, indicated having used the drug in the previous year.

“The low cost of and ease of access to nitrous oxide make it a popular recreational drug, especially among younger people,” writes Dr. Cyrille De Halleux, a specialist in internal medicine, critical care and resident at The Hospital for Sick Children (SickKids) and chief fellow in the Division of Clinical Pharmacology and Toxicology at the University of Toronto, Toronto, Ontario.

Chronic use of nitrous oxide can cause functional vitamin B12 deficiency, which can result in long-term health effects, especially neurological consequences. The three most common presentations of toxicity are damage to the spinal cord (myelopathy), nerve damage affecting strength and sensation (neuropathy) and behavioural abnormalities (encephalopathy). Treatment includes stopping the use of the substance, vitamin B12 supplementation and methionine.

“Clinicians should enquire about nitrous oxide use in patients with unexplained findings suggestive of vitamin B12 deficiency or other compatible neurologic symptoms,” the authors conclude.

Reference:

Cyrille De Halleux and David N. Juurlink, Diagnosis and management of toxicity associated with the recreational use of nitrous oxide,DOI: https://doi.org/10.1503/cmaj.230196.