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

Neurological Effects of Stimulants and Hallucinogens

In this article, we will discuss the history, pharmacodynamics, and neurotoxicity of psychostimulants and hallucinogens. The drugs discussed are widely used and have characteristic toxidromes and potential for neurological injuries with which the practicing clinician should be familiar. Psychostimulants are a class of drugs that includes cocaine, methamphetamine/amphetamines, and cathinones, among others, which produce a crescendoing euphoric high. Seizures, ischemic and hemorrhagic strokes, rhabdomyolysis, and a variety of movement disorders are commonly encountered in this class. Hallucinogens encompass a broad class of drugs, in which the user experiences hallucinations, altered sensorium, distorted perception, and cognitive dysfunction. The experience can be unpredictable and dysphoric, creating a profound sense of anxiety and panic in some cases. Recognizing the associated neurotoxicities and understanding the appropriate management is critical in caring for these patient populations. Several of these agents are not detectable by standard clinical laboratory analysis, making identification and diagnosis an even greater challenge.

Treatment Seeking Nitrous Oxide Users in Addiction Care: A Comparison with Cocaine Users on Clinical and Treatment Characteristics

INTRODUCTION

Over the past decade, frequent use of large quantities of nitrous oxide (N2O) has become more common in the Netherlands. Although N2O poses several negative health consequences for a subgroup of problematic N2O users, there is a lack of knowledge on what characterizes these intensive users. This study therefore aims to provide the demographic and substance use characteristics and experiences during treatment of treatment seeking problematic N2O users and to compare this with a matched group of treatment-seeking problematic cocaine users.

METHODS

A retrospective chart review was performed of patients who were referred for treatment of problematic N2O use at a large Dutch addiction care facility from January 2020 to September 2022, extracting demographics, pattern of use and follow-up data. Additionally, a subgroup of N2O users was propensity-score matched (1:1) with a subgroup of treatment seeking problematic cocaine users, both groups excluding users with substance use disorders or frequent use of substances other than N2O and cocaine, respectively.

RESULTS

128 patients with a N2O use disorder were included in the total sample and a subgroup of 77 N2O-only users was propensity-score matched on age and sex to 77 cocaine-only users. N2O users were typically young (mean age 26.2 years), male (66.4%), unmarried (82.9%), with a low education level (59.0%) and born in the Netherlands (88.2%), with parents born in Morocco (45.3%). N2O was used intermittently (median 10 days/month, IQR 4.0-17.5 days) and often in very large quantities (median 5 kg [ca. 750 balloons] per average using day, IQR 2-10 kg). Compared to the patients with a cocaine use disorder, matched N2O users were lower educated, more often from Moroccan descent, and less likely to be alcohol or polysubstance users. Despite receiving similar treatments, N2O users were twice as likely to discontinue treatment before completion compared to cocaine users (63 vs. 35%, p = 0.004).

CONCLUSION

Treatment-seeking problematic N2O users are demographically different from treatment-seeking problematic cocaine users and are much more likely to dropout from psychological treatment. Further research is needed into the needs and other factors of problematic N2O users that relate to poor treatment adherence in problematic N2O users.

Quantitative determination of nitrous oxide in human blood by HS-GC-MS: forensic application of two fatal poisoning cases

Nitrous oxide (N2O), also known as laughing gas, has a euphoric effect and is becoming increasingly popular as a recreational inhalant drug. Deaths caused by recreational nitrous oxide abuse are rare, but may still occur. Although some methods for the quantification of N2O by GC-MS have been reported, elimination of carbon dioxide interference and the choice of a suitable internal standard remain current limitations to accurate N2O quantification. Here, a validated method using headspace-gas chromatography-mass spectrometry (HS-GC-MS) is described that allows the quantification of N2O in human blood samples: sodium hydroxide is used to remove carbon dioxide, and n-pentane is chosen as a suitable internal standard. Collectively, the validation results show a good linear relationship of N2O in blood within the concentration range of 0.02 ∼ 0.5 mL/mL and an LOD of 0.005 mL/mL. Subsequent application of the validated method to two real mortality cases due to N2O intoxication provided reference values for blood concentrations in forensic cases. Other biological specimens (gaseous samples and tissues) of the deceased were also analyzed to demonstrate that the deaths were caused by asphyxia due to the inhalation of N2O.

Multidisciplinary rehabilitation following recreational nitrous oxide (N2O) misuse: evaluating service provision and rehabilitation outcomes in a cohort with serious disability

Purpose: Recreational nitrous oxide (N2O) misuse is increasing globally. Chronic misuse can cause neurological impairments that require rehabilitation, though literature characterising rehabilitation is limited. This study aimed to evaluate rehabilitation service provision for impairments resulting from N2O misuse. Methods: A retrospective audit of hospitalised patients referred for rehabilitation for N2O toxicity was conducted between 2015 and 2022 at a single metropolitan hospital. Data were collected via medical record audit and analysed via descriptive and non-parametric statistics. Results: 16 eligible cases were identified, aged 18-43 years (50% female/male), with increasing case frequency. 12 cases received inpatient rehabilitation episodes for multifactorial sensorimotor, cognitive and psychosocial impairments. Cases articulated diverse rehabilitation goals and received intervention from a median of 6 clinical disciplines. All cases required assistance to mobilise or perform self-care activities on admission. Functional Independence Measure (FIM) scores significantly improved with rehabilitation (median FIM 84[75-93] to 117[112-123], p < .001). Despite gains in independence, all cases required referral for ongoing rehabilitation post-discharge. Conclusions: Demand for inpatient rehabilitation for disabling N2O toxicity appears to be increasing. In this series, cases were young, exhibited serious impairments, and had multidisciplinary rehabilitation needs. Inpatient rehabilitation led to significant functional improvements, though ongoing disability was evident post-discharge.

The Role of Cobalamin in Multiple Sclerosis: An Update

Multiple sclerosis (MS) is a neurodegenerative condition that results in axonal and permanent damage to the central nervous system, necessitating healing owing to autoimmune reactions and persistent neuroinflammation. Antioxidant and anti-inflammatory drugs are essential for the management of oxidative stress and neuroinflammation. Additionally, multivitamin supplementation, particularly vitamin B12 (cobalamin), may be beneficial for neuronal protection. Although there is no documented connection between vitamin B12 deficiency and MS, researchers have explored its potential as a metabolic cause. This review highlights the therapeutic benefits of cobalamin (Cbl) in patients with MS.

Nitrous Oxide as an Emerging Cause of Subacute Combined Degeneration and Polyneuropathy: A Two-Case Report

Recreational use of nitrous oxide (N2O), commonly known as laughing gas, has increased in the last few years, bringing an increase in the number of reported cases of toxicity due to this gas. Subacute combined degeneration (SCD) of the spinal cord is the most frequently reported neurological disorder due to the use of N2O, as well as polyneuropathy and even psychiatric symptoms. All of these disorders are consequences of a functional deficit of vitamin B12. We are reporting the cases of two patients with a history of N2O abusive use presenting to the emergency department with progressive symptoms of paresthesia, ascending symmetric paraparesis, and gait ataxia, emulating the clinical characteristics of Guillain-Barré Syndrome (GBS). In both cases, magnetic resonance imaging (MRI) showed findings compatible with transverse myelitis of the cervical spinal cord, and electrodiagnosis studies reported the presence of polyneuropathy with a mixed mechanism. All these findings together pointed to the presence of myeloneuropathy due to a vitamin B12 deficit induced by the prolonged use of N2O. Symptoms improved gradually with vitamin B12 supplementation and abstinence from N2O. It is important to acknowledge the clinical characteristics of complications due to neurotoxicity induced by N2O. Such complications are potentially reversible if they are treated appropriately and quickly. Considering the increase in N2O abuse, it should be considered a probable cause when treating patients with myelopathy and/or neuropathy of an unusual etiology.

Vitamin B12 Supplementation in Psychiatric Practice

PURPOSE OF REVIEW

Vitamin B12 (B12, cobalamin) deficiency has been associated with neuropsychiatric symptoms, suggesting a role for B12 supplementation both as a treatment for psychiatric symptoms due to B12 deficiency and as an augmentation strategy for pharmacological treatments of psychiatric disorders. This critical review discusses the major causes of B12 deficiency, the range of psychiatric and non-psychiatric manifestations of B12 deficiency, the indications for testing B12 levels, and the evidence for B12 supplementation for major psychiatric disorders.

RECENT FINDINGS

We find that high-quality evidence shows no benefit to routine B12 supplementation for mild depressive symptoms or to prevent depression. There is very limited evidence on the role of B12 supplementation to augment antidepressants. No high-quality evidence to date suggests a role for routine B12 supplementation in any other major psychiatric disorder. No formal guidelines indicate when clinicians should test B12 levels for common psychiatric symptoms, in the absence of major risk factors for deficiency or cardinal symptoms of deficiency. No robust evidence currently supports routine B12 supplementation for major psychiatric disorders. However, psychiatrists should be aware of the important risk factors for B12 deficiency and should be able to identify symptoms of B12 deficiency, which requires prompt testing, medical workup, and treatment. Testing for B12 deficiency should be considered for atypical or severe psychiatric presentations.

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.

A case of functional vitamin B12 deficiency after recreational nitrous oxide use

The recreational use of nitrous oxide as laughing gas becomes a real public health issue among adolescents and young adults. Chronic use is deleterious and can lead to severe neurological disorders. Nitrous oxide inactivates vitamin B12, and the functional defect of vitamin B12 plays a major role in the pathogenesis of nitrous oxide-related neurological disorders. Here we report the case of a 22-year-old woman who came to the hospital after an unexplained loss of consciousness. She exhibited typical features of vitamin B12 or folate deficiency such as macrocytic anemia and hypersegmented neutrophils. However, serum concentrations of folate and vitamin B12 were normal. In contrast, circulating concentrations of total homocysteine and methylmalonic acid were significantly increased. These results clearly indicated a defect in vitamin B12 functions. The reason for this defect was clarified when she revealed that she had been consuming nitrous oxide recreationally for over a year. The present case points out the challenges in diagnosing vitamin B12 deficiency in the context of nitrous oxide abuse due to normal concentrations of total serum vitamin B12 in a significant proportion of cases. The medical community should be aware of how difficult it can be to interpret B12 status in this specific population.

Functional vitamin B12 deficiency is a consistent feature in hospital admissions for neurological disorders due to the use of nitrous oxide

Introduction: Misuse of inhaled nitrous oxide is a growing concern in France. It is known to alter concentrations of vitamin B12, which is required as a cofactor for methionine synthase and methylmalonyl-CoA mutase activity. Hence, measurement of the concentrations of cobalamin metabolism biomarkers, including vitamin B12, homocysteine, and methylmalonic acid, could assist in the management of patients with a complex clinical presentation or in those who deny the consumption of nitrous oxide.Methods: We retrospectively collected clinical and biological data in patients hospitalized for nitrous oxide use in a university hospital in southern France between January 2020 and October 2022.Results: Thirty-one patients were identified during 34 months; 79% were men with a median age of 23.7 years. Most (97%) presented with peripheral polyneuropathy and/or myelopathy. The median vitamin B12 concentration was 134.6 pmol/L, with 17 of 31 patients having values less than 145 pmol/L (the lower limit of the normal range). The median plasma folate concentration was 20.1 nmol/L, which is within the normal range. The median plasma homocysteine concentration was 87.7 µmol/L (normal range <15 µmol/L), and the median plasma methylmalonic acid concentration was 3.8 µmol/L (normal range <0.5 µmol/L).Conclusion: Nitrous oxide use is an emerging public health problem in France, as shown by the number of patients admitted to our hospital. The presence of a functional vitamin B12 deficiency was a consistent feature that could be helpful in diagnosis in complex cases.

Use of the Rehabilitation Treatment Specification System (RTSS) in the management of nitrous oxide (N2O)-induced spinal cord injury

Nitrous oxide (N₂O) is an inhaled anaesthetic gas and a popular intoxicant. Excessive recreational use can cause spinal cord myelopathy. Previous studies have discussed the medical management. However, none have specified the sensorimotor rehabilitation management. This case report documents the investigations, physical rehabilitation and functional outcomes in two cases of N₂O-associated myelopathy. Both presented with lower limb strength and sensorimotor integration impairments resulting in ataxic ambulation. Dorsal column signal abnormality was observed on T2-weighted MRI in one case. Myelopathy was diagnosed based on clinical presentation and both were treated with vitamin B₁₂ Rehabilitation was conceived and specified using the Rehabilitation Treatment Specification System (RTSS). Both cases achieved independent indoor gait on hospital discharge, and full function at 9 months in one case. Appropriate and timely medical management and reasoned rehabilitation provided excellent functional outcomes for N₂O-related myelopathy. By using the RTSS, reasoned rehabilitation efficacy can be tested in the future.