Clinical epidemiological characteristics of nitrous oxide abusers: A single-center experience in a hospital in China

Rare but relevant: Nitrous oxide and peripheral neurotoxicity, what do we know?

Nitrous oxide (N2O), used medically as an anaesthetic, has gained popularity as a recreational drug, with rising prevalence particularly among young adults. While its reinforcing and addictive potential remains debated, N2O is proven to be neurotoxic, especially with prolonged, heavy use, which is often unexpected for users. The neurotoxicological mechanism underlying N2O-induced neurotoxicity involves inactivation of vitamin B12 (cobalamin), which disrupts methionine synthesis, essential for maintaining the myelin sheath. This can result in demyelinating diseases, including generalized demyelinating polyneuropathy (GDP). Clinical incidence of N2O-induced peripheral neuropathy is largely unknown, although some research suggests it is not uncommon. Treatment includes immediate cessation of N2O use and vitamin B12 supplementation. Although this treatment often reverses damage, residual symptoms such as limb weakness may persist. Additionally, genetic and dietary factors, such as vitamin B12 deficiency, may heighten individual vulnerability for N2O's detrimental effects.

Severe subacute combined degeneration of the spinal cord resulting from nitrous oxide (N2O) abuse: a case series

OBJECTIVE

To describe the demographic, clinical, laboratory, and radiological findings, and the clinical course of seven patients with severe N2O-induced subacute combined degeneration of the spinal cord (SACD).

METHODS

Retrospective study with prospective follow-up of patients with SACD associated with N2O abuse presenting at a single center between 2014 and 2024.

RESULTS

The median age (range) of the seven patients (one woman, six men) was 24 (18-33) years. Prior to disease onset, patients had consumed N2O daily over a median (range) of 12 (3-20) weeks, with a mean (SD; range) inhalation dosage of 2376.7 (2872.7; 160-9000) g of N2O per day. Clinical presentations included paresthesia and paresis in the legs and gait disturbances. All patients exhibited characteristic signal alterations in the posterior columns spanning from C1 to T10 on T2-weighted spinal MRIs. Electrophysiology demonstrated polyneuropathies in all but one patient. Vitamin B12 levels were decreased in four, but normal in three patients. Methylmalonic acid levels were elevated in all patients. Although the median (interquartile range [IQR]) modified Rankin Scale score improved from 3.0 (3.0-4.0) at baseline to 1.0 (1.0-2.0; p < 0.05, Wilcoxon matched-pairs signed-rank test) at follow-up after the start of vitamin B12 supplementation, all five patients who could be examined on follow-up exhibited persistent deficits on the last follow-up assessment at a median (range) of 5 (3-116) months after disease onset.

CONCLUSIONS

N2O abuse over a few weeks can lead to severe SACD. The diagnosis is supported by characteristic findings on spinal MRI and elevated methylmalonic acid levels, while normal vitamin B12 levels do not rule out N2O-induced SACD. Although there was some clinical improvement upon cessation of N2O abuse and vitamin B12 supplementation, residual deficits persisted.

Nitrous Oxide-Induced Vitamin B12 Deficiency and Myelopathy in Whippets Abusers: A Report of Two Cases

Whippets abuse, prevalent among recreational drug users, poses significant health risks, particularly through the inactivation of vitamin B12 by nitrous oxide (N2O). This deficiency can lead to myelopathy, resulting in serious neurological complications. We present two female patients, aged 22 and 35, with a history of regular whippet use over the past three years, who exhibited clinical symptoms of myelopathy, including motor weakness, rigidity, sensory changes, and gait abnormalities. The 35-year-old patient showed weakness and swelling in her legs; magnetic resonance imaging (MRI) revealed no acute findings, but lab results indicated a critically low serum vitamin B12 level (102 pg/mL), elevated homocysteine (44 µmol/L), and high methylmalonic acid (29,054 nmol/L). She improved with vitamin B12, vitamin D supplementation, and physical and occupational therapy. The 22-year-old patient reported progressive stiffness and tingling, with MRI revealing T2 hyperintensities in the brain and longitudinal T2 hyperintensities in the posterior spinal cord; her vitamin B12 level was 180 pg/mL, and she responded positively to supplementation and physical therapy. These cases underscore the risk of nitrous oxide-induced myelopathy associated with vitamin B12 deficiency among whippet users. Early recognition and intervention are essential to prevent irreversible neurological damage, and routine screening for vitamin B12 deficiency in this population is recommended. Further research is needed to explore the long-term implications of N2O abuse.

Nitrous oxide abuse in a 21-year-old female: a case report and review of literature

The abuse of nitrous oxide (N2O) poses a substantial public health challenge. In many countries, including China, regulations governing the utilization and accessibility to N2O remain ambiguous, particularly within the food industry. Here, we report a case of a 21-year-old female who presented with symptoms of subacute combined degeneration (SCD) of the spinal cord due to N2O abuse. The patient exhibited bilateral lower limb numbness and weakness, low serum vitamin B12 levels with elevated homocysteine levels, and lumbar spine magnetic resonance imaging (MRI) revealed abnormal signals of the spinal cord. Following cessation of N2O and comprehensive therapy including methylcobalamin and nerve growth factor, the symptoms significantly improved. A follow-up examination 3 months later showed good progress in gait stability. At a 5-year follow-up, the patient's previous clinical symptoms had completely disappeared, and her quality of life had returned to normal. This case underscores the urgency of raising awareness and prevention of N2O abuse, emphasizing the importance of timely diagnosis and comprehensive treatment for patient recovery. Clear formulation and enforcement of relevant regulatory measures are equally crucial in reducing instances of abuse.

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: Clinical Outcomes, Pharmacology, Pharmacokinetics, Toxicity and Impact on Metabolism

The recreational use of nitrous oxide (N2O), also called laughing gas, has increased significantly in recent years. In 2022, the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) recognized it as one of the most prevalent psychoactive substances used in Europe. Chronic nitrous oxide (N2O) exposure can lead to various clinical manifestations. The most frequent symptoms are neurological (sensitive or motor disorders), but there are also other manifestations like psychiatric manifestations or cardiovascular disorders (thrombosis events). N2O also affects various neurotransmitter systems, leading to its anesthetic, analgesic, anxiolytic and antidepressant properties. N2O is very challenging to measure in biological matrices. Thus, in cases of N2O intoxication, indirect biomarkers such as vitamin B12, plasma homocysteine and plasma MMA should be explored for diagnosis and assessment. Others markers, like oxidative stress markers, could be promising but need to be further investigated.

Nitrous Oxide Inhalant Abuse: Preliminary Results from a Cross-Sectional Study on Knowledge, Attitudes, and Practices of Italian Physicians (2023)

Background and Objectives: Nitrous oxide (N2O) has recently emerged as a cheap alternative to other recreational substances. Although legally available, its chronic use is associated with severe neurological and hematological complications due to the irreversible inactivation of vitamin B12. While no reliable data on abuse of N2O in Italy have been provided to date, we assessed the knowledge, attitudes, and practices of Italian medical professionals on the management of N2O abuse cases. Materials and Methods: A cross-sectional study was performed as a web-based survey through a series of Facebook discussion groups (targeted medical professionals: 12,103), and participants were specifically asked about their previous understanding of N2O abuse and whether they had or not any previous experience in this topic. Results: A total 396 medical professionals participated in the survey. Overall, 115 participants had previous knowledge about N2O abuse (29.04%), with higher odds for professionals with a background in emergency medicine (adjusted odds ratio (aOR) 3.075; 95% confidence intervals (95%CI) 1.071 to 8.828) and lower for specialists in psychiatry (aOR 0.328; 95%CI 0.130 to 0.825). Knowledge status on N2O abuse was largely unsatisfying, as knowledge status, reported as a percent value, was estimated to 45.33% ± 24.71. Having previously managed a case of N2O abuse was associated with higher risk perception of the actual severity of this condition (aOR 5.070; 95%CI 1.520 to 16.980). Conclusions: Our study suggests that N2O poisoning cases are occurring in Italian settings but are not reasonably reported to national authorities. As substantial knowledge gaps of Italian medical workforces were identified, we cannot rule out that the actual abuse of N2O in the population may be far larger than currently suspected.

A Case of Subacute Combined Degeneration Secondary to Recreational Whippet Use

'Whippets' or nitrous oxide (N2O) abuse is a rare etiology of B12 deficiency and subacute combined degeneration (SCD). Often used in the medical field as an anesthetic, recreational use has rapidly increased given its euphoric effects. Easy accessibility over the counter at local stores due to the fact that it has bacteriostatic effects useful for canisters of creams and perishable goods. This makes N2O, or "laughing gas," easy to obtain. Long-standing abuse of N2O can lead to deleterious effects on the central nervous system, including SCD, polyneuropathy, and death. Presentation includes frequent falls, ataxic gait, weakness in the lower extremities, and neuropathy. Herein, we present a case of a 25-year-old male with no past medical history presenting with SCD in the setting of longstanding recreational whippet use. Our case highlights an important consideration for all specialties, including emergency medicine, psychiatry, family medicine, and internal medicine physicians.

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.

Severe length-dependent peripheral polyneuropathy in a patient with subacute combined spinal cord degeneration secondary to recreational nitrous oxide abuse: A case report and literature review

Nitrous oxide abuse can have detrimental effects on the central and peripheral nervous systems. This case study report aims to demonstrate a combination of severe generalized sensorimotor polyneuropathy and cervical myelopathy related to vitamin B₁₂ deficiency following nitrous oxide abuse. We present a clinical case study and literature review examining primary research-published between 2012 and 2022-reporting nitrous oxide abuse affecting the spinal cord (myelopathy) and peripheral nerves (polyneuropathy); 35 articles were included in the review with a total of 96 patients, where the mean "patients" age was 23.9 years and were in a 2:1 male/female ratio. Of the 96 cases, within the review, 56% of patients were diagnosed with polyneuropathy, most commonly impacting the nerves of the lower limb (62%), while 70% of patients were diagnosed with myelopathy, most commonly impacting the cervical region (78%) on the spinal cord. In our clinical case study, a 28-year-old male underwent a multitude of diagnostic investigations for bilateral "foot drop" and sense of lower limb stiffness as ongoing complications of a vitamin B₁₂ deficiency secondary to recreational nitrous oxide abuse. Both the literature review and our case report emphasize the dangers of recreational nitrous oxide inhalation, colloquially termed "nanging" and the risks it presents to both the central and peripheral nervous systems, which is erroneously considered by many recreational drug users to be less harmful than other illicit substances.

Case report: Recreational nitrous oxide abuse triggered peripheral neuropathy possibly through the immune-mediated pathogenesis

Nitrous oxide (N2O), commonly known as laughing gas, is widely used in clinical practice and food industry. However, an increasing number of young people have been abusing N2O for recreational purpose, resulting in many functional disorders and sometimes irreversible nerve damage. We present the case of a 20-year-old N2O abuser who gradually developed peripheral neuropathy after continuously inhaling N2O for 2 months. The neurological symptoms of the patient had kept exacerbation for the next 2 months until she came for medical care sitting in a wheelchair. We suggested the patient halting N2O intake and supplementing methylcobalamine according to the standardized protocol. Her symptoms had partly recovered during the following 2 weeks but remained unchanged in another 2 weeks. Antibodies against ganglioside complexes were detected and anti-GM1 IgM antibodies were positive in both cerebrospinal fluid and serum. Intravenous immunoglobulin was given as an additional treatment and the patient's symptoms had significantly recovered further. The patient discharged walking by herself. Then she has been continuously followed up in outpatient department for the next 4 months and taking steroid hormone as well as methylcobalamine. Her symptoms gradually disappeared and all the electrophysiological parameters significantly improved. With this case we were able to show that N2O-related peripheral neuropathy is not only a metabolic disorder but also an immune-mediated disease. N2O intake can trigger a mimic Guillain-Barré syndrome.

Clinical epidemiological characteristics of nitrous oxide abusers: A single-center experience in a hospital in China

PURPOSE

This study investigated the clinical epidemiological characteristics of nitrous oxide (N₂ O) abusers in a hospital in China, which have not been systematically reported.

METHODS

The characteristics of patients abusing N₂ O who were examined and treated at the Affiliated Hospital of Xuzhou Medical University from January 2017 to December 2020 were analyzed.

RESULTS

A total of 61 patients (average age: 21.7 ± 3.2 years; 42 male and 19 female) were enrolled; 60.7% of the patients had an education level of high school or lower, and most (59.0%) had no stable occupation. The mean exposure time was 8.5 ± 7.7 months (range: 1-36 months). Only 52.5% of the abusers reported the physician of the relevant exposure history at the first time of visiting the doctor. The main clinical type was mixed (49.2%). The most common clinical manifestation was distal limb numbness (80.3%). The most frequent outcome was peripheral neuropathy (59%) and subacute combined degeneration (36%). Serum homocysteine level was elevated in 67.5% (27/40) of the patients, while 44.4% (20/45) showed reduced vitamin B12. Note that 61% (22/36) showed abnormal signals in the posterior or lateral funiculus of the spinal cord, and 97% (31/32) of the patients showed peripheral nerve damage by electromyography. In all cases, symptoms were alleviated after halting N₂ O intake and receiving nutritional neurotherapy.

CONCLUSIONS

N₂ O abuse can lead to nervous system damage, especially peripheral nerve and spinal cord damage. A full understanding of its clinical epidemiological characteristics is helpful for clinicians to make a timely and clear diagnosis.