In Ireland and internationally, there has been much attention on the growing popularity of nitrous oxide. In response, the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) has published a report on nitrous oxide in Europe in order to increase awareness and to help stakeholders prepare for and respond to public health and social threats associated with nitrous oxide.1 As part of the EMCDDA report, the Health Research Board (HRB) compiled a case report on the current situation regarding nitrous oxide in Ireland.

Control status of nitrous oxide
Nitrous oxide is not currently a controlled substance under Ireland’s Misuse of Drugs Act 1977 and can be legally sold for catering and industrial purposes. The Criminal Justice (Psychoactive Substances) Act 2010 prohibits the sale, importation, or exportation of psychoactive substances and under this legislation it is illegal to sell nitrous oxide for its psychoactive properties.

Prevalence of nitrous oxide use
As prevalence of nitrous oxide use is not routinely collected in Ireland’s National Drug and Alcohol Survey, it is not possible to provide population prevalence estimates. The only source of data on adult nitrous oxide use is the Irish results of the 2021 European Web Survey on Drugs (EWSD),2 which surveyed adults aged 18 years and over who had used illicit drugs in the last year. Of the 4,398 EWSD respondents who answered the question on nitrous oxide use, 1.1% reported last-month use and a further 3.7% had used nitrous oxide in the last year. In total, 23.3% had ever used nitrous oxide. Respondents aged 18–24 years were most likely to have used nitrous oxide in the last year (see Table 1).

Of those who reported last-year use of nitrous oxide, 89% reported infrequent use (1–11 days) and 11% reported occasional use (12–51 days); there were no sex or age group differences. On a typical day that nitrous oxide was used, 21.1% used no more than one canister, while 26.3% used at least 10 (see Table 2).

Table 1: Most recent use of nitrous oxide among Irish respondents in the European Web Survey on Drugs, by sex and age group

Table 2: Number of canisters typically used on a day that nitrous oxide is used, by sex and age group

Nitrous oxide use among young people
The Planet Youth Survey conducted among post Junior Certificate students in schools in North County Dublin in 2021 collected data on nitrous use among young people (<18 years).3 The questions on nitrous oxide were answered by 2,384 respondents. The main results were:

• 6.2% of young males and 5.3% of young females had ever used nitrous oxide.
• There were no significant differences in use by sex in the overall sample.
• Males attending 5th year had a significantly greater lifetime prevalence of use (11.9%).
• Heavy use (more than 40 lifetime uses) was low, at 1% for males and 0% for females.

Nitrous oxide use in festival settings
A 2019 online survey of 1,193 Irish festival attendees aged 18 years and over found that 28% had used nitrous oxide while attending music festivals in Ireland in the last year. Of those who had attended music festivals abroad (n=619), 38% had used nitrous oxide. Respondents to this survey typically used stimulant ‘club drugs’ mainly as part of a polydrug use pattern.4

Availability of nitrous oxide
To assist with the EMCDDA report, Merchants Quay Ireland undertook a short survey of 15 member organisations of the National Voluntary Drug and Alcohol Sector (NVDAS). None of the respondents had robust data concerning prevalence. However, 12 respondents stated that nitrous oxide was available in their area: eight believed it had increased in popularity in the last year, with four believing its popularity had remained the same. The sporadic nature of its popularity was also highlighted – respondents reported that it can be very prevalent for a number of months at a time and that it is particularly prevalent on weekends, midterm breaks, and bank holidays.

Regarding availability, one Dublin respondent noted that it is available in large blue bottles for €100 per bottle and also in smaller capsules that cost €50 per box. Young people arrange to buy it from a local nitrous oxide dealer as most shops will not sell it to them, despite being available in some discount shops.

Another respondent reported a difference in cost between online purchases, where it costs 30 cent per canister, and street purchases, where it can cost €2–€5 per canister. Respondents viewed nitrous oxide as a drug primarily used by younger people who also use other drugs. Two respondents identified a couple of distinct groups and contexts: early teens who use nitrous oxide in parks and wastelands and older teens who use it at house parties. It was noted that there is a growing trend for people in their early twenties to use it at parties or ‘preloading’ before going out.

Harms associated with nitrous oxide
Requests for information were submitted to a number of sources in order to assess the extent of nitrous oxide-related harm in Ireland. These were the National Drug Treatment Reporting System (NDTRS), the National Drug-Related Deaths Index (NDRDI), the Hospital In-Patient Enquiry (HIPE) scheme, and emergency departments.

In mid-2020, in response to anecdotal reports of increased use, the NDTRS added nitrous oxide to its system. In 2020, less than five episodes of treatment were reported. Preliminary data from 2021 indicate that 10 episodes of treatment were reported. The majority of these cases were male and the mean age was 16 years. All were new cases that had never received treatment before and most were polydrug users who also reported problem use of cannabis. The NDRDI recorded no drug poisoning deaths due to nitrous oxide for the period 2004–2017 inclusive. Data for 2018 onwards are not yet available.

In the HIPE scheme, poisoning by nitrous oxide falls under the ICD-10-AM code T41.0 – poisoning by inhaled anaesthetics. As this code is used for poisoning by any inhaled anaesthetic, it is not specific to nitrous oxide. However, analysis of discharges from 2018 to 2020 indicates that in this three-year period there were less than five discharges with a T41.0 diagnosis. A case report was published in 2022 describing the presentation of two young males to the emergency department of a large urban university hospital in Dublin with progressive neurological dysfunction related to nitrous oxide use.5 A case with subacute combined degeneration of the cord secondary to nitrous oxide use has also been reported by a hospital in Dublin.

Conclusion
While the information presented here would indicate that the prevalence of nitrous oxide use in Ireland is relatively low and that, to date, low levels of nitrous oxide-related harm have been reported, the recreational use of nitrous oxide is a growing public health concern. It will be important to continue to monitor trends in nitrous oxide into the future and therefore respond to changes in its use.

1    European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) (2022) Recreational use of nitrous oxide: a growing concern for Europe. Luxembourg: Publications Office of the European Union. https://www.drugsandalcohol.ie/37506

2    Mongan D, Killeen N, Evans D, Millar SR, Keenan E and Galvin B (2022) European Web Survey on Drugs 2021: Irish results. Dublin: Health Research Board. https://www.drugsandalcohol.ie/36571/

3    North Dublin Regional Drug and Alcohol Task Force (NDRDATF) (2022) ‘Improving health outcomes by understanding the lived experiences of young people in North Dublin’. Planet Youth Report 1. Dublin: Merlin Press.
https://www.drugsandalcohol.ie/36972/

4    Ivers J-H, Killeen N and Keenan E (2022) Drug use, harm-reduction practices and attitudes toward the utilisation of drug safety testing services in an Irish cohort of festival-goers. Ir J Med Sci, 191: 1701–1710. https://www.drugsandalcohol.ie/34860/

5    McCormick JP, Sharpe S, Crowley K, et al. (2023) Nitrous oxide-induced myeloneuropathy: an emerging public health issue. Ir J Med Sci, 192: 383–388. https://www.drugsandalcohol.ie/35688/