Leaflet Details
| Title | Entonox |
| Department | Inpatient Pain Service |
| Author(s) | Monica Thompson |
| Review Date | November 2025 |
| Next Review | November 2027 |
| Download | A5 Booklet PDF |
| Accessibility Options | Click on the Recite Me button to show our accessibility resources |
Patient Information
What is Entonox
Entonox is a gas that may be offered to help you manage pain during certain procedures, such as dressing changes or applying a plaster cast.
It is made up of 50% oxygen and 50% nitrous oxide. Although nitrous oxide is sometimes used as an anesthetic, in this mixture it acts as fast acting pain relief.
Entonox is often referred to as ‘gas and air’ and is most used for pain relief during labour.
As Entonox is short acting, it can be used for any procedure that requires brief pain relief, or to provide comfort while you wait for other pain medications to take effect.
Are there any side effects?
Entonox may cause drowsiness and a feeling of light-headedness. Other possible side effects include dizziness, nausea, and dry mouth.
These effects usually fade quickly once you stop using Entonox. Most patients find that by continuing to use it and focusing on slow, steady breathing, they soon become accustomed to these sensations.
However, if you find during practice that you do not like the effects of Entonox, inform the person supervising you, and an alternative form of pain relief can be provided.
How do I use it?
Before you are given Entonox, a nurse will go through a checklist with you to ensure it is safe and suitable for you.
Please inform the nurse if you:
- Have, or have recently had, an ear infection or ear surgery
- Have been scuba diving recently
- Are pregnant or think you may be pregnant
- Have emphysema or other long-term breathing conditions (such as chronic bronchitis or chronic asthma)
You will be shown the Entonox equipment and given an opportunity to practise before the treatment begins.
Once you start, you can choose when to use it and how often.
Entonox is self-administered, giving you complete control over your pain relief.
You should begin using Entonox 1-2 minutes before the procedure starts to allow it time to take effect. For the best results, breathe slowly and slightly deeper than normal.
You may also become very sleepy. A nurse will be with you all the time when you are using Entonox and will take it away if this happens. You will wake up very quickly after the Entonox is stopped.
What can I do afterwards?
The effects of Entonox usually wear off quickly, but you should take care when standing or walking until you feel steady on your feet.
You must wait at least 30 minutes before driving. This waiting time may be longer if you have received other medications that can make you drowsy. Before leaving, you will be asked to sign a form confirming that you feel safe and competent to drive.
Please inform the nurse if you continue to experience pain after you stop using Entonox.
Is there an alternative?
If Entonox is not suitable for you, the nursing and medical team will discuss other pain relief options.
What are the risks and benefits of using Entonox?
The risks associated with Entonox use are very low. The main concern is the possibility of the gas becoming trapped within the body, which can occur only in certain medical conditions. Nurses will carry out a thorough assessment beforehand and will not administer Entonox if there is any risk of this happening.
Benefits
Entonox offers fast-acting pain relief with very few aftereffects.
Find out more ...
If you have any questions or concerns regarding pain relief either before or after your operation or procedure, and would like to discuss these, then please contact the Inpatient Pain Service.
We are available:
Monday to Friday between 08.00 and 18.00 hours
Telephone the hospital switchboard on 01932 872000 and ask for pager 5042
Additional information about Entonox can be found at https://www.bocgases.co.uk/pages/healthcare
