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.

Nitrous oxide induced subacute combined degeneration of the spine cord: A case report

RATIONALE

In recent years, recreational use of inhaled nitrous oxide (N2O) is on the increase among young people, accompanied by a corresponding rise in reports about its toxicity. Subacute combined degeneration of the spine cord (SCD) is the typical clinical picture of the nervous system disorder caused by N2O intoxication, as a result of metabolic disturbance of vitamin B12.

PATIENT CONCERNS, DIAGNOSES, INTERVENTIONS AND OUTCOMES

We report a 28-year-old female of SCD due to prolonged use of N2O, presented with paresthesia and unsteady in walking progressing within 1 month. Symptoms gradually improved with the treatment of intramuscular injections of hydroxocobalamin combined with N2O abstinence, and the patient recovered completely with normal neurological examination after 4 months of follow-up.

LESSONS

Clinicians should be aware of the clinical features and pathogenesis of SCD caused by N2O intoxication in order to lead effective treatment as soon as possible. Recreational N2O use should always be considered as an etiology when dealing with patients presented with myelopathy and/or neuropathy suspected of vitamin B12 deficiency.

Vitamin B12 Status in Recreational Users of Nitrous Oxide: A Systematic Review Focusing on the Prevalence of Laboratory Abnormalities

The recreational use of nitrous oxide (N₂O) as "laughing gas" is a growing problem. The chronic toxicity of N₂O is mainly due to its ability to oxidize vitamin B12, making it dysfunctional as a cofactor in metabolic pathways. This mechanism plays a major role in the development of neurological disorders in N₂O users. The assessment of vitamin B12 status in N₂O users is important but challenging due to the lack of decrease in total vitamin B12 in most cases despite genuine vitamin B12 functional deficiency. Other biomarkers, such as holotranscobalamin (holoTC), homocysteine (tHcy) and methylmalonic acid (MMA), are interesting candidates to properly assess vitamin B12 status. Here, we conducted a systematic review of case series in order to assess the prevalence of abnormal values of total vitamin B12, holoTC, tHcy and MMA in recreational N₂O users, which is an important prerequisite for determining the best screening strategy in future guidelines. We included 23 case series (574 N₂O users) from the PubMed database. Total circulating vitamin B12 concentration was low in 42.2% (95% confidence interval 37.8-46.6%, n = 486) of N₂O users, while 28.6% (7.5-49.6%, n = 21) of N₂O users had low circulating concentrations of holoTC. tHcy levels were elevated in 79.7% (75.9-83.5%, n = 429) of N₂O users, while 79.6% (71.5-87.7%, n = 98) of N₂O users had increased concentrations of MMA. In summary, the increases in tHcy and MMA were the most prevalent abnormalities, and should be measured alone or in combination in symptomatic N₂O users rather than total vitamin B12 or holoTC.

Nitrous Oxide-Induced Subacute Combined Degeneration in a 38-Year-Old Pregnant Female After Recreational Use

Nitrous oxide (N2O) misuse creates a diagnostic dilemma due to its clinical presentation, difficulty in identification, and toxicity related to its chronic abuse, with resultant morbidity and mortality. Chronic abuse can lead to myeloneuropathy and subacute combined degeneration in otherwise healthy individuals. Health professionals should be aware of the commercial availability and abuse of N2O by the public, and N2O toxicity should be included in the differential diagnosis in patients presenting with myelopathy of unknown etiology. A case report was conducted on a 38-year-old female at approximately 30 weeks of gestation who presented to the emergency department with worsening bilateral lower extremity numbness, tingling, and weakness. The patient admitted to nitrous oxide inhalation during the two months prior to admission. She reported using four cans of whippets per week (approximately 8 g of N2O per whippet) up to 50 cans per day (400 g N2O) prior to the onset of symptoms. An MRI of the cervical spine was performed, showing T2 hyperintensity from C2 to C6 involving dorsal columns indicative of subacute combined degeneration. The patient was treated with intravenous vitamin B12 due to the clinical and radiographic evidence of nitrous oxide-induced myelopathy. The pathophysiology of N2O toxicity involves the oxidation of the cobalt atom of cobalamin (vitamin B12) from its reduced active 1+ valent state to its oxidized inactive 3+ valent state. This oxidation inactivates the enzyme methionine synthetase. B12 is an essential cofactor for downstream DNA synthesis. Consequently, excess N2O creates functional B12 deficiency leading to irreversible nerve damage if left undiagnosed and untreated.

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

BACKGROUND

Since 2000, the prevalence of recreational nitrous oxide (N₂O) use has increased in the Western world. Although N₂O is a relatively safe drug, the overall increase in the use of N₂O has concomitantly also initiated a modest but important increase in the number of young excessive users. The recent introduction of large 2 kg N₂O tanks, allowing high and prolonged dosing, has facilitated this excessive use. This is of concern, because repeated exposure to high doses of N₂O for a prolonged time is known to induce neurological damage, such as (irreversible) neuropathy and paralysis due to N₂O-induced vitamin B₁₂ deficiency. The increasing trend of recreational users with N₂O-induced neurological damage at emergency departments confirms the urgency of this development.

OBJECTIVE/METHODS

This narrative review describes recent trends in N₂O use and misuse, the adverse health effects associated with excessive use and the risk factors of excessive use.

RESULTS

Considering the rising trend in N₂O use, particularly among young and other vulnerable people, we propose to take legislative action to limit the availability of N₂O, and also advocate for better and timely education of non-users, users and medical professionals about the serious side-effects associated with excessive N₂O use.

CONCLUSION

It is concluded that the increase in excessive N₂O use is of serious concern.

Nitrous oxide-induced reproductive risks: Should recreational nitrous oxide users worry?

BACKGROUND

Nitrous oxide (N₂O) is a frequently used anaesthetic. Since the year 2000, recreational use of N₂O, also known as 'laughing gas', became popular as a recreational drug due to its mild psychedelic effect. In the 1980s, several reports warned against N₂O-induced reproductive risks among healthcare personnel, questioning the occupational safety of N₂O in health care.

METHODS

Data about the reproductive risks of N₂O were collected from literature.

RESULTS

Particularly in the past, professionals working in dental and midwifery practices, operating theatres and ambulance transport were exposed to high levels of N₂O. Adverse reproduction effects included congenital anomalies, spontaneous abortion and reduced fertility rates in females. Following occupational measures, like maximal exposure limits for ambient N₂O, this occupational risk was considerably reduced. Recreational users of N₂O, however, voluntarily and repeatedly expose themselves to (very) high doses of N₂O. As such, they exceed the health exposure limits some hundred times, but they are fully unaware of the related reproductive risks.

CONCLUSION

We advocate to increase the awareness in recreational N2O-users about its potential reproductive risks, especially in heavy users, pregnant users or those who intend to become pregnant.

Nitrous oxide abuse induced subacute combined degeneration despite patient initiated B12 supplementation

INTRODUCTION

Nitrous oxide (N₂O) is a commonly used inhaled anesthetic that is legal to purchase as a food additive and is popular as a recreational euphoric drug. Abuse causes a functional B12 deficiency, leading to clinical features and imaging consistent with subacute combined spinal cord degeneration (SCD).

CASES

Poison Center medical records from four patients are reviewed in this series. Four patients presented with lower extremity weakness, paresthesias and gait abnormalities in the setting of chronic N₂O abuse. Each reported using 50-150 N₂O cartridges ("whippets") almost daily for months to years, and reported supplementing with oral B12 at the recommendation of other users and online forums. None reported prior B12 deficiency or dietary restrictions, and none exhibited hematologic abnormalities.

RESULTS

All patients had clinical signs of neurotoxicity including weakness and ataxia. Additionally, all had elevated methylmalonic acid and homocysteine concentrations with normal B12 indicating a functional B12 deficiency. Three had imaging consistent with SCD despite home supplementation The MRI in the fourth case was inconclusive due to movement artifact.

CONCLUSION

We report four cases of subacute combined degeneration induced by recreational nitrous oxide abuse despite self-administered vitamin B12 supplementation.

Recreational Nitrous Oxide-Induced Subacute Combined Degeneration of the Spinal Cord

There is rising use of recreational nitrous oxide (N₂O) in the community because of its availability as “whippet” canisters. Nitrous oxide use is still legal and outside the purview of the Drug Enforcement Administration (DEA). It is not detected on a routine drug screen, and patient history is key to establishing the diagnosis. We highlight a case of subacute combined degeneration in a young patient secondary to recreational nitrous oxide use, which improved with vitamin B12 replacement. A 19-year-old male with a history of recreational nitrous oxide use presented with progressive bilateral lower extremity paresthesia and ataxia. Neurological examination revealed deficits in vibration and proprioception, motor weakness, and diminished reflexes in the bilateral lower extremities. The laboratory results were significant for pancytopenia, profound vitamin B12 deficiency (55 ng/mL), and elevated methylmalonic acid (2.14 umol/L). The urine drug screen was negative. MRI showed subacute degeneration of the spinal cord dorsal column at C2-C5. Treatment with intramuscular cyanocobalamin resulted in the normalization of pancytopenia and B12 levels (573 ng/mL). The patient had partial resolution of neurological symptoms following the initiation of parenteral vitamin B12 replacement. The mechanism of subacute combined degeneration in the setting of nitrous oxide toxicity appears to be mediated by functional B12 deficiency. Oxidation of cobalt ion of vitamin B12 by nitrous oxide renders it unavailable as a coenzyme, leading to the accumulation of by-products that enter lipid metabolism, resulting in abnormal myelin synthesis, which ultimately manifests as subacute combined degeneration. Vitamin B12 deficiency of unclear etiology should raise suspicion for nitrous oxide toxicity as early initiation of replacement therapy with vitamin B12 can improve neurological function.

Does vitamin B12 deficiency explain psychiatric symptoms in recreational nitrous oxide users? A narrative review

Background Recreational use of nitrous oxide (N₂O) is associated with many side effects, of which neurological complications are most common. Nitrous oxide abuse is also associated with psychiatric symptoms, but these have received less attention so far. Vitamin B12 deficiency may play a role in the development of these psychiatric symptoms.Aims To explore the relationship among the occurrence of recreational nitrous oxide-induced psychiatric symptoms, accompanying neurological symptoms, vitamin B12 status and choice of treatment.Methods A retrospective search for case reports was conducted across multiple databases (Pubmed, Embase, Web of Science, PsycINFO and CINAHL). Keywords included variants of "nitrous oxide", "case report" and "abuse". No restrictions to language or publication date were applied.Results The search retrieved 372 articles. A total of 25 case reports were included, representing 31 patients with psychiatric complications following nitrous oxide abuse. The most often reported symptoms were: hallucinations (n = 16), delusions (n = 11), and paranoia (n = 11). When neurological symptoms were present, patients were treated more frequently with vitamin B12 supplementation.Conclusions This review highlights the need to recognize that psychiatric symptoms may appear in association with nitrous oxide use. Approximately half of the cases that presented with nitrous oxide-induced psychiatric complaints did not show neurological symptoms, and their vitamin B12 concentration was often within the hospital's reference range. Psychiatrists and emergency physicians should be aware of isolated psychiatric symptoms caused by recreational nitrous oxide abuse. We suggest asking all patients with new psychiatric symptoms about nitrous oxide use and protocolizing the management of nitrous oxide-induced psychiatric symptoms.

Problematic Use of Nitrous Oxide by Young Moroccan-Dutch Adults

The recreational use of nitrous oxide (N2O; laughing gas) has largely expanded in recent years. Although incidental use of nitrous oxide hardly causes any health damage, problematic or heavy use of nitrous oxide can lead to serious adverse effects. Amsterdam care centres noticed that Moroccan–Dutch young adults reported neurological symptoms, including severe paralysis, as a result of problematic nitrous oxide use. In this qualitative exploratory study, thirteen young adult Moroccan–Dutch excessive nitrous oxide users were interviewed. The determinants of problematic nitrous oxide use in this ethnic group are discussed, including their low treatment demand with respect to nitrous oxide abuse related medical–psychological problems. Motives for using nitrous oxide are to relieve boredom, to seek out relaxation with friends and to suppress psychosocial stress and negative thoughts. Other motives are depression, discrimination and conflict with friends or parents. The taboo culture surrounding substance use—mistrust, shame and macho culture—frustrates timely medical/psychological treatment of Moroccan–Dutch problematic nitrous oxide users. It is recommended to use influencers in media campaigns with the aim to decrease the risks of heavy nitrous oxide use and improve treatment access. Outreach youth workers can also play an important role in motivating socially isolated users to seek medical and or psychological help.

A new mechanistic approach for the treatment of chronic neuropathic pain with nitrous oxide integrated from a systems biology narrative review

The limitations of the currently available treatments for chronic neuropathic pain highlight the need for safer and more effective alternatives. The authors carried out a focused review using a systems biology approach to integrate the complex mechanisms of nociception and neuropathic pain, and to decipher the effects of nitrous oxide (N₂O) on those pathways, beyond the known effect of N₂O on N-methyl-D-aspartate receptors. This review identified a number of potential mechanisms by which N₂O could impact the processes involved in peripheral and central sensitization. In the ascending pathway, the effects of N₂O include activating TWIK-related K⁺ channel 1 potassium channels on first-order neurons, blocking voltage-dependent calcium channels to attenuate neuronal excitability, attenuating postsynaptic glutamatergic receptor activation, and possibly blocking voltage-dependent sodium channels. In the descending pathway, N₂O induces the release of endogenous opioid ligands and stimulates norepinephrine release. In addition, N₂O may mediate epigenetic changes by inhibiting methionine synthase, a key enzyme involved in DNA and RNA methylation. This could explain why this short-acting analgesic has shown long-lasting anti-pain sensitization effects in animal models of chronic pain. These new hypotheses support the rationale for investigating N₂O, either alone or in combination with other analgesics, for the management of chronic neuropathic pain.

Nitrous oxide causes peripheral neuropathy in a dose dependent manner among recreational users

BACKGROUND

Nitrous oxide (N₂O) has been used in clinical and recreational settings for over 150 years. Through inactivation of the Vitamin B12 dependent enzyme, methionine synthase, N₂O can lead to the development of peripheral neuropathy. This study sought to determine the relationship between the exposure and risk of neurological symptoms in the largest ever sample of users.

DESIGN

Data are drawn from the Global Drug Survey (GDS) over three consecutive years (2014-2016). The Global Drug Survey is an online, cross-sectional survey of substance use, translated into multiple languages.

PARTICIPANTS

Respondents to the Global Drug Survey who provided details on N₂O use and the experience of paraesthesia in the previous 12 months.

MEASUREMENTS

Questions relating to N₂O use, peripheral neuropathy, age and gender were explored among last year's users.

FINDINGS

Of 241,566 respondents, 41,181 (17.0%) indicated that they had ever used nitrous oxide; of these, 42.1% had used in the last 12 months. For the final model, data from 16,124 participants who had used N₂O in the last 12 months and had provided responses on age, dose, gender and paraesthesia were used. Of these, the number of respondents reporting persistent numbness/tingling (paraesthesia) in their hands or feet was 537 (3.3%). Although the risk was very low among infrequent users, there was a strong dose-response relationship. For people indicating one or two doses per session, the probability of reporting paraesthesia was approximately 0.018 by comparison; for people indicating 100 doses per session the probability was approximately 0.085. The association, between dose and paraesthesia was influenced by gender and age.

CONCLUSION

While infrequent, episodic users are not at risk, a minority of heavy users are at dose-dependent risk of developing serious neurological consequences. Better education and raised awareness of early symptoms are required.

Subacute Combined Spinal Cord Degeneration by Recreational Laughing Gas (N2O) Use

Background:

A few young patients were brought in with subacute combined spinal cord degeneration at the Department of Neurology in our hospital. They all have used laughing gas for recreational purposes.

Case:

A 30-year-old woman, known with alcohol abuse, was presented to our Department of Neurology for having paresthesia and unstable movements of arms, legs, and trunk for 9 days. She has used 50 laughing gas patterns per day. The diagnosis of laughing gas–induced combined spinal cord degeneration was evident by the low count of vitamin B₁₂ combined with lesions shown on magnetic resonance imaging (MRI). Abstaining from the laughing gas, weekly intramuscular injections of hydroxocobalamin and revalidation, she was fully recovered in 8 weeks.

Conclusions:

Recreational use of laughing gas seems to be more used in our society, however, without having any knowledge of the neurological consequences. The right diagnosis and treatment can provide full recovery in these patients. Furthermore, attention for this diagnosis can help increase social awareness.

No Laughing Matter: Presence, Consumption Trends, Drug Awareness, and Perceptions of "Hippy Crack" (Nitrous Oxide) among Young Adults in England

In clinical settings, nitrous oxide gas is a safe anesthetic used during childbirth, in dentistry, and to relieve anxiety in emergencies. Colloquially known as "hippy crack"' or "laughing gas," it is increasingly taken recreationally for its euphoric and relaxing effects and hallucinogenic properties. Using a self-reported survey, we gathered quantitative and qualitative information on users and non-users of hippy crack among a young population regarding: consumption patterns, knowledge, risk awareness and intentions toward future abuse. Quantitative responses from a total of 140 participants were analyzed for frequencies and relationships, whereas qualitative data were evaluated via identifying the reoccurring themes. Overall, 77.1% (n = 108) had heard of hippy crack and 27.9% (n = 39) admitted to past-year use. Prior users mostly indicated intended future use, had an average low number of past-year uses but some with > 20 occasions, had a varied number of inhalations per occasion (often 1-10) with an effect lasting up to 5 min, and a majority preferred social rather than lone use. For non-users, 79.2% said they would take hippy crack with the vast majority (94%) preferring a social setting. The results show a concerning gap between available evidence and awareness of side effects. Despite serious reported side effects, including psychosis and myeloneuropathy-especially on the young developing brain-only a minority (29.3%) was aware of any side effects. In contrast, in a hypothetical scenario depicting a first social encounter with hippy crack, the qualitative responses were in contrast to qualitative outcomes revealing that participants would try (n = 30)/not try (n = 25) it, would feel under pressure to try it (n = 6) with only 11 opting to exit the situation. In summary, this first report of trends and perceptions of the use of hippy crack among young adults in the England highlights a lack of concern with side effects, coupled to a willingness to partake. Because typical users are young with risks to the still developing brain, education about the nitrous oxide abuse is warranted to prevent impaired brain development. Further studies to investigate the possible effects of nitrous oxide on the developing brain in young adults would advance meaningful prevention.

Psychiatric comorbidities in a young man with subacute myelopathy induced by abusive nitrous oxide consumption: a case report

Nitrous oxide (N₂O), a long-standing anesthetic, is known for its recreational use, and its consumption is on the rise. Several case studies have reported neurological and psychiatric complications of N₂O use. To date, however, there has not been a study using standardized diagnostic procedures to assess psychiatric comorbidities in a patient consuming N₂O. Here, we report about a 35-year-old male with magnetic resonance imaging confirmed subacute myelopathy induced by N₂O consumption, who suffered from comorbid cannabinoid and nicotine dependence as well as abuse of amphetamines, cocaine, lysergic acid diethylamide, and ketamine. Additionally, there was evidence of a preceding transient psychotic and depressive episode induced by synthetic cannabinoid abuse. In summary, this case raises awareness of an important mechanism of neural toxicity, with which physicians working in the field of substance-related disorders should be familiar. In fact, excluding N₂O toxicity in patients with recognized substance-related disorders and new neurological deficits is compulsory, as untreated for months the damage to the nervous system is at risk of becoming irreversible.

Ketamine potentiates cerebrocortical damage induced by the common anaesthetic agent nitrous oxide in adult rats

For general anaesthesia, patients usually receive a combination of drugs, all of which are classified as gamma-amino-butyric acid (GABA) agonists, with two notable exceptions - ketamine and nitrous oxide (laughing gas, N(2)O) - which are antagonists of N-methyl-D-aspartate (NMDA) glutamate receptors. At clinically relevant doses both ketamine and N(2)O, like other NMDA antagonists, have the potential to induce psychotomimetic reactions in humans and to cause pathomorphological changes in cerebrocortical neurons in rat brain. Because drug combinations used in clinical anaesthesia sometimes include both ketamine and N(2)O, we undertook experiments to evaluate whether augmented neurotoxicity results from their combined use. Ketamine and N(2)O were administered alone or in combination by various dosing regimens to adult female rats for a duration of 3 h and the severity of cerebrocortical neurotoxic changes was quantified histologically. Because GABA agonists are known to protect against the psychotomimetic and neurotoxic effects of NMDA antagonists, we also evaluated whether the combined neurotoxicity of ketamine+N(2)O can be prevented by certain commonly used GABA agonists. When ketamine and N(2)O were used in combination the neurotoxic reaction was enhanced to a degree much greater than can be explained by simple additivity. The apparent synergistic interaction was particularly striking when low doses of the agents were combined, the degree of toxic synergism at higher doses being masked by a ceiling effect. GABA agonists protected against ketamine/N(2)O neurotoxicity. It is recommended that this information be taken into consideration in the selection of drugs to be used in multi-agent protocols for general anaesthesia.