Increasing recreational nitrous oxide use: Should we worry? A narrative review

Mechanisms and recent advances in the diagnosis and treatment of nitrous oxide-induced peripheral neuropathy: a narrative review

Under standard conditions, nitrous oxide (N2O) manifests as a colorless, odorless gas with a mildly sweet taste. The compound finds applications in various fields, including its use as an aerosol propellants, an accelerant in motor racing, and an anesthetic in surgical procedures and dentistry. Unfortunately, the recreational misuse of N2O has become prevalent among young individuals due to its euphoric and hallucinogenic effects. Compounding this issue is the fact that nitrous oxide can be easily obtained from over-the-counter household items, facilitating its non-medical use. The global community has witnessed a surge in the recreational utilization of nitrous oxide gas in recent years. Despite the widespread non-medical abuse of N2O, there remains inadequate understanding of the potential adverse effects resulting from exposure to it. This paper provides an overview of management findings, laboratory and electrodiagnostic characteristics, as well as clinical presentations associated with neurological disorders induced by nitrous oxide usage.

Does nitrous oxide addiction exist? An evaluation of the evidence for the presence and prevalence of substance use disorder symptoms in recreational nitrous oxide users

BACKGROUND

Prevalence of nitrous oxide (N2 O) use appears to be increasing in numerous countries worldwide, and excessive use has been associated with physical and mental problems. Because there currently is no consensus whether N2 O has addictive potential, we aimed to evaluate the evidence for the presence and prevalence of DSM-5 substance use disorder (SUD) symptoms in N2 O users.

ANALYSIS

A literature search was conducted to assess the evidence for the presence of any of the 11 DSM-5 SUD symptoms in N2 O users and the prevalence experiencing those symptoms. A substantial part of the studied N2 O users use more than intended (i.e. 46% to 98%) and spend a substantial amount of time using N2 O. At least some of the studied N2 O users experience interpersonal problems (i.e. 13% to 80%) and use N2 O in risky situations, such as driving under the influence. Evidence for the other criteria is either insufficient or inconclusive.

CONCLUSIONS

The literature base for the presence and prevalence of DSM-5 substance use disorder (SUD) symptoms in nitrous oxide (N2 O) users is limited and largely consists of qualitative studies and case studies, but it provides consistent evidence for the presence of at least four SUD criteria in heavy N2 O users. N2 O could well be addictive and should be treated as a potentially addictive substance until systematic assessments can provide evidence-based guidance to users, healthcare professionals and legislators.

Nitrous oxide abuse direct measurement for diagnosis and follow-up: update on kinetics and impact on metabolic pathways

Recreational use of nitrous oxide (N2O) has become a major health issue worldwide, with a high number of clinical events, especially in neurology and cardiology. It is essential to be able to detect and monitor N2O abuse to provide effective care and follow-up to these patients. Current recommendations for detecting N2O in cases of recreational misuse and consumption markers are lacking. We aimed to update current knowledge through a review of the literature on N2O measurement and kinetics. We reviewed the outcomes of experiments, whether in preclinical models (in vitro or in vivo), or in humans, with the aim to identify biomarkers of intoxication as well as biomarkers of clinical severity, for laboratory use. Because N2O is eliminated 5 min after inhalation, measuring it in exhaled air is of no value. Many studies have found that urine and blood matrices concentrations are connected to ambient concentrations, but there is no similar data for direct exposure. There have been no studies on N2O measurement in direct consumers. Currently, patients actively abusing N2O are monitored using effect biomarkers (biomarkers related to the effects of N2O on metabolism), such as vitamin B12, homocysteine and methylmalonic acid.

Ketamine and the neurobiology of depression: Toward next-generation rapid-acting antidepressant treatments

Ketamine has emerged as a transformative and mechanistically novel pharmacotherapy for depression. Its rapid onset of action, efficacy for treatment-resistant symptoms, and protection against relapse distinguish it from prior antidepressants. Its discovery emerged from a reconceptualization of the neurobiology of depression and, in turn, insights from the elaboration of its mechanisms of action inform studies of the pathophysiology of depression and related disorders. It has been 25 y since we first presented our ketamine findings in depression. Thus, it is timely for this review to consider what we have learned from studies of ketamine and to suggest future directions for the optimization of rapid-acting antidepressant treatment.

Neuropsychiatric disorders associated with recreational nitrous oxide use

BACKGROUND

Recreational nitrous oxide use has grown in popularity among young people and has become a serious public health problem. Chronic use of nitrous oxide can lead to a functional vitamin B12 deficiency and neuropsychiatric complications.

PURPOSE

This study aimed to investigate the characteristics of neuropsychiatric complications associated with nitrous oxide use and to enhance clinicians' awareness of this public health problem.

METHODS

We retrospectively reviewed 16 patients with neuropsychiatric disorders related to nitrous oxide use who were treated in our hospital from June 2021 to October 2022. Their demographics, clinical features, investigations, treatments and outcomes were analyzed.

RESULTS

There were ten males and six females between the ages of 17 and 25 with a mean age of 20.5 ± 2.6 years. Thirteen patients sought medical help from the neurology clinic. Two patients presented to the psychiatric department and one patient presented to the emergency department with acute cognitive impairment. All 16 patients presented with neurological symptoms, such as paresthesia in four limbs or the lower limbs, unsteady gait and weakness. Twelve patients developed psychiatric symptoms, such as hallucinations, agitation, depression, emotional indifference and personality changes. Twelve patients had vitamin B12 deficiency. All 16 patients had hyperhomocysteinemia. Fourteen patients showed abnormal high signal on T2-weighted imaging and an inverted "V" sign in axial view, mainly involving the cervical cord. Neuropsychiatric symptoms improved with vitamin B12 treatment and cessation of nitrous oxide use in all cases.

CONCLUSION

Young adults are predominately involved in recreational use of nitrous oxide, which can cause neuropsychiatric complications. The clinical response to vitamin B12 supplementation and cessation of nitrous oxide use is generally good. Clinicians should recognize nitrous oxide use as a public health problem and a cause of a wide range of neuropsychiatric symptoms, particularly in younger patients.

Lethal nitrous oxide (N2O) intoxication during surgery: the contribution of immunohistochemistry in identifying the cause of death: a case report

BACKGROUND

Nitrous oxide (N2O) is a gas used in medicine for its analgesic, anxiolytic and amnesic properties. It is a drug considered safe if adequately administered. In the literature, accidental N2O-related deaths are rare. They are mostly related to inhalation of this substance for recreational and autoerotic purposes; rarely are reported deaths due to incorrect administration of medical gas in anesthesia. The diagnosis of death from acute N2O intoxication is complex and is generally an exclusion diagnosis: the macroscopic and microscopic post-mortem signs are entirely nonspecific. Furthermore, the circumstantial data are not always supportive and can even be confusing, mainly if the death occurred inside a hospital.

CASE PRESENTATION

We describe a particular case of death from acute nitrous oxide poisoning in a hospital environment, of a Caucasian male of 72-years-old. The intoxication occurred during a minimally invasive vascular surgery due to an incorrect assembly of the supply lines of medical gases (O2 and N2O). The identification of the cause of death resulted from the analysis of circumstantial data, macroscopic and microscopic autoptic findings, and immunohistochemical investigations based on the search for antibodies anti E-selectin, P-selectin, and HIF 1-α.

CONCLUSION

Although not pathognomonic of asphyxiation by N2O, the latter molecules are a valid and early marker of hypoxic insult. Therefore, in concert with all other findings, it may constitute valid support for the forensic pathologist to ascertain the cause of death in case of suspected intoxication by N2O.

Mechanisms Involved in the Neurotoxicity and Abuse Liability of Nitrous Oxide: A Narrative Review

The recreational use of nitrous oxide (N₂O) has increased over the years. At the same time, more N₂O intoxications are presented to hospitals. The incidental use of N₂O is relatively harmless, but heavy, frequent and chronic use comes with considerable health risks. Most importantly, N₂O can inactivate the co-factor cobalamin, which, in turn, leads to paresthesia's, partial paralysis and generalized demyelinating polyneuropathy. In some patients, these disorders are irreversible. Several metabolic cascades have been identified by which N₂O can cause harmful effects. Because these effects mostly occur after prolonged use, it raises the question of whether N₂O has addictive properties, explaining its prolonged and frequent use at high dose. Several lines of evidence for N₂O's dependence liability can be found in the literature, but the underlying mechanism of action remains controversial. N₂O interacts with the opioid system, but N₂O also acts as an N-methyl-D-aspartate (NMDA) receptor antagonist, by which it can cause dopamine disinhibition. In this narrative review, we provide a detailed description of animal and human evidence for N₂O-induced abuse/dependence and for N₂O-induced neurotoxicity.

Becoming a nitrous oxide user on social media: Learning to maximise pleasures and minimise harms

BACKGROUND

In his classic work 'Becoming a marihuana user', Howard Becker (1953) showed how drug use learning occurred in social interactions and settings, which in turn shape drug use. Today, social media offers people opportunities to learn about drugs without physical proximity. In this paper, we identify nitrous oxide (N₂O) users' key concerns about how to maximise pleasures and minimise harms, as expressed on the social media platform Reddit. In doing so, we consider what learning about N₂O online might mean for the provision of drug education in an era of internet technology.

METHOD

Data are drawn from a Reddit page (subreddit) dedicated to N₂O use. We undertook thematic analysis of 655 threads contributed in late-2020. The subreddit is conceptualised as an internet-mediated social world that constitutes drug user knowledges, practices and identities, rather than simply reflecting them.

RESULTS

Our analysis uncovers practices not previously been reported in academic literature or health information on N₂O, such as breathing techniques to maximise the effects and use of filters to reduce exposure to oil residue. While education resources often describe effects as 'mild', users recounted intense pleasures including euphoria, anaesthesia, sensory distortion, hallucination and epiphanies, especially when N₂O was used with other drugs. Subreddit members were deeply concerned to minimise the risk of harms. Yet official health advice regarding N₂O was not referenced, some misinterpretation of scientific literature was apparent and drug treatment was almost never suggested when people recounted harms.

CONCLUSION

In contrast to official health resources, the subreddit offers members practical advice on harm reduction. It provides opportunities for users of N₂O to position themselves as playful, informed and caring curators of drug use pleasures. We highlight the need for those formulating drug education to engage with the knowledge, practices and identities that emerge within internet-mediated social worlds.