What is Entonox?

Entonox has been available for many years and is an excellent method of providing short-term pain relief and relaxation during procedures that may cause some discomfort.

Entonox consists of two gases, 50 per cent nitrous oxide and 50 per cent oxygen. When combined with oxygen, nitrous oxide can be used to relieve pain. It is sometimes called ‘gas and air’ and is most commonly used by women during childbirth.

It is self-administered by a mouth piece, giving you complete control over the timing of the pain relief.

Are there any side effects?

Entonox can make you feel drowsy and light-headed. Other effects may include dizziness, nausea, and a dry mouth. All of these sensations disappear rapidly when you stop using Entonox.

Most patients find they quickly get used to these sensations after using it for a short while. However, if you decide you do not like the effects you can stop using it at any time.

You may become sleepy, however a healthcare professional will be with you at all times when using the Entonox. They can remove the mouth piece if necessary and you will wake up quickly.

How do I use it?

Before you are given Entonox the healthcare professional will complete an assessment checklist with you to make sure that it is appropriate for you to use. You will be shown the equipment and be able to practice before the procedure. You will remain in control of its use and decide when and how often you wish to use it. To get the best effect you need to take slow breaths, slightly deeper than normal.

What can/can’t I do afterwards?

After using Entonox the sensation will wear off quickly but we advise you to rest for 30 minutes after you stop using Entonox.

You MUST NOT drive for 30 minutes after using Entonox – this is a legal requirement and you will not be covered by your motor insurance if you do so.


There is minimal risk in taking Entonox. One concern is that the gas may get trapped in the body, however, this is only a potential problem in very specific medical conditions. Before you can be offered this form of pain relief you will be assessed to see if you are suitable.

If we are able to offer Entonox, you will be asked to sign a consent form. If you have any other questions or require further information or advice, please contact:

Clinician Seen:

Ref: 27-19-105
Review: 07/21