Nitrous oxide 50% / Oxygen 50%
Available from a pharmacy with pharmacist advice
Lowest controls; includes some codeine preparations
Legal requirements and restrictions
Preparations containing controlled drugs in low concentrations. Subject to minimal controls - mainly invoicing requirements.
Legal requirements
- No special prescription requirements
- No controlled drugs register required
- No safe custody requirements
- Invoices must be retained for 2 years
Other medicines in this category
Codeine linctus, Co-codamol (low strength), Kaolin and morphine
Official documents, adverse reaction reporting, and safety monitoring
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Official medicine documents
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Drug safety updates
MHRA alerts for Nitrous oxide + Oxygen
Safety monitoring data
Yellow Card reports
The MHRA Yellow Card scheme collects reports of suspected side effects from healthcare professionals and patients. View the Drug Analysis Profile (iDAP) for real-world adverse reaction data.
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Submit a Yellow Card report to the MHRA
Data from the MHRA Yellow Card scheme. A reported reaction does not necessarily mean the medicine caused it. Contains public sector information licensed under the Open Government Licence v3.0.
EudraVigilance
The European Medicines Agency (EMA) collects suspected adverse reaction reports from across the EU/EEA through the EudraVigilance system. Search for safety data on this medicine.
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EudraVigilance data is published by the European Medicines Agency (EMA). A suspected adverse reaction is not necessarily caused by the medicine.
22 branded products available
MHRA licensed products
View all licensed products for Nitrous oxide + Oxygen on the MHRA register
Entonox cylinders size D
Entonox cylinders size EA with integral headset
Entonox cylinders size ED with integral headset
Entonox cylinders size EW
Entonox cylinders size EX with integral headset
Entonox cylinders size F
Entonox cylinders size G
Therapeutically similar medicines
Similarity is based on WHO Anatomical Therapeutic Chemical (ATC) classification and on a factual NHS dm+d therapeutic-grouping code prefix. Source data: NHS dm+d via TRUD (OGL v3.0), WHO ATC/DDD Index.
NHS prescribing volume and spending trends
Guidelines from the National Institute for Health and Care Excellence
NICE clinical guidance(8)
Sedation in under 19s: using sedation for diagnostic and therapeutic procedures (CG112)
Fractures (non-complex): assessment and management (NG38)
End-tidal Control software for use with Aisys closed circuit anaesthesia systems for automated gas control during general anaesthesia (MIB10)
Cytokine adsorption devices for treating respiratory failure in people with COVID-19 (MIB217)
CytoSorb therapy for sepsis (MIB87)
ERBE flexible cryoprobes for bronchoscopic diagnosis and treatment (MIB39)
Intrapartum care (NG235)
Shiley Endotracheal Tube with TaperGuard Cuff for intensive care patients at risk of ventilator‑associated pneumonia (MIB22)
Source: National Institute for Health and Care Excellence (NICE). Contains public sector information licensed under the Open Government Licence v3.0.
Check stock at pharmacies and supply information
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Search for this medicine at major UK pharmacy chains. These links open the retailer's own website — results depend on their current online catalogue.
Supply & safety information
Official UK regulator monitoring and safety alerts
Pharmacy links redirect to the retailer's own search and do not represent real-time stock levels. Shortage and safety information sourced from MHRA drug safety updates (gov.uk, Crown Copyright under OGL v3.0).
Codes for healthcare professionals and prescribing systems
These codes are used by healthcare IT systems and prescribers to identify this medicine.
NHS UK identifiers
Browse tools
SNOMED CT and dm+d codes from NHS TRUD (Technology Reference data Update Distribution), licensed under the Open Government Licence v3.0. ATC codes from the WHO Collaborating Centre for Drug Statistics Methodology (whocc.no).
Active and completed clinical studies from ClinicalTrials.gov
Source: ClinicalTrials.gov, a database of the U.S. National Library of Medicine (NLM), National Institutes of Health (NIH). Data accessed via ClinicalTrials.gov API v2. Trial information is provided for research purposes and does not constitute medical advice.
Academic studies and reviews for this medicine's active substance
Showing the 50 most relevant studies.
Reviews & meta-analyses: 11 · Randomised trials: 22 · 1949–2026
Showing the 50 most relevant studies, sorted by most relevant.
N. Wrage-Mönnig, M. Horn, R. Well, et al.
Soil Biology and Biochemistry, 2018
A. Quick, W. J. Reeder, Tiffany B. Farrell, et al.
Earth-Science Reviews, 2019
Arcari S, Moscati M, Giuca MR, et al.
2025
- Oxygen
- Nitrous Oxide
- Anesthetics, Inhalation
Wang W, Meng X, Zhao Y, et al.
2026
- Pain
- Burns
- Nitrous Oxide
Mroczek M, Orlanska A
2026
I. Thakur, Kristina Medhi
Bioresource technology, 2019
Tang W, Fortin SG, Intrator N, et al.
2025
- Oxygen
- Ammonia
- Nitrous Oxide
Rossit M, Gil-Manich V, Ribera-Uribe JM
2021
The aim of this systematic review was to determine the success rate of nitrous oxide-oxygen procedural sedation (NOIS) in dentistry. A systematic digital search was conducted for publications or reports of randomized controlled trials evaluating the clinical performance of NOIS. Abstracts of research papers were screened for suitability, and full-text articles were obtained for those who met the inclusion and exclusion criteria accordingly. The quality of the studies was assessed using the revised Cochrane risk-of-bias tool (RoB 2). A total of 19 articles (eight randomized clinical trials with parallel intervention groups and 11 crossover trials), published between May 1988 and August 2019, were finally selected for this review. The studies followed 1293 patients reporting NOIS success rates, with a cumulative mean value of 94.9% (95% CI: 88.8-98.9%). Thirteen trials were conducted on pediatric populations (1098 patients), and the remaining six were conducted on adults (195 patients), with cumulative efficacy rates of 91.9% (95% CI: 82.5-98.1%) and 99.9% (95% CI: 97.7-100.0%), respectively. The difference was statistically significant (P = 0.002). Completion of treatment and Section IV of the Houpt scale were the most used efficacy criteria. Within the limitations of this systematic review, the present study provides important information on the efficacy rate of NOIS. However, further well-designed and well-documented clinical trials are required and there is a need to develop guidelines for standardization of criteria and definition of success in procedural sedation. Currently, completion of treatment is the most used parameter in clinical practice, though many others also do exist at the same time. To maximize NOIS efficacy, clinicians should strictly consider appropriate indications for the procedure.
Abstract licence: CC BY-NC
Thomas PS, Dave BH, Shah DJ, et al.
2023
Zhang JJ, Yu P, Dang H, et al.
2024
- Hematologic Neoplasms
- Procedural Pain
- Pain
BackgroundPatients with hematological malignancies received multiple hypodermic injections of recombinant human granulocyte colony-stimulating factor. Procedural pain is one of the most common iatrogenic causes of pain in patients with hematological malignancies. It is also identified as the most commonly occurring problem in clinical care in the Department of Hematology and Oncology at Shenzhen University General Hospital. However, providing immediate relief from pain induced by hypodermic injection of recombinant human granulocyte colony-stimulating factor remains a major challenge. This trial aims to evaluate the safety and analgesic efficacy of a fixed nitrous oxide/oxygen mixture for patients with hematological malignancies and experiencing procedural pain caused by hypodermic injection of recombinant human granulocyte colony-stimulating factor in the department.MethodsThe nitrous oxide/oxygen study is a single-center, randomized, double-blind, placebo-controlled trial involving patients with hematological malignancies who require hypodermic injections of recombinant human granulocyte colony-stimulating factor for treatment. This trial was conducted in the Hematology and Oncology Department of Shenzhen University General Hospital. A total of 54 eligible patients were randomly allocated to either the fixed nitrous oxide/oxygen mixture group (n = 36) or the oxygen group (n = 18). Neither the investigators nor the patients known about the randomization list and the nature of the gas mixture in each cylinder. Outcomes were monitored at the baseline (T0), immediately after hypodermic injection of recombinant human granulocyte colony-stimulating factor (T1), and 5 min after hypodermic injection of recombinant human granulocyte colony-stimulating factor (T2) for each group. The primary outcome measure was the score in the numerical rating scale corresponding to the highest level of pain experienced during hypodermic injection of recombinant human granulocyte colony-stimulating factor. Secondary outcomes included the fear of pain, anxiety score, four physiological parameters, adverse effects, total time of gas administration, satisfaction from both patients and nurses, and the acceptance of the patients.DiscussionThis study focused on the safety and analgesic efficacy during hypodermic injection of recombinant human granulocyte colony-stimulating factor procedure. Data on the feasibility and safety of nitrous oxide/oxygen therapy was provided if proven beneficial to patients with hematological malignancies during hypodermic injection of recombinant human granulocyte colony-stimulating factor and widely administered to patients with procedural pain in the department.Trial registrationChinese Clinical Trial Register, ChiCTR2200061507. Registered on June 27, 2022. http://www.chictr.org.cn/edit.aspx?pid=170573&htm=4.
Abstract licence: CC BY
Sources: aggregated from Europe PMC (EMBL-EBI), OpenAlex, Crossref, PubMed and other open scholarly databases. Retracted articles are excluded. Study information is provided for research purposes and does not constitute medical advice.
Scientific data (pharmacology, interactions, ADME) is not yet available for this medicine. Clinical sections are sourced from the NHS dm+d database.