Advice after your nerve block for surgery
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What is Entonox?
Entonox is a mixture of 50% oxygen and 50% nitrous oxide, also known as ‘gas and air’ or ‘laughing gas’. It is often used to treat pain during childbirth. It is also used widely by the ambulance service and in hospitals for a variety of procedures and conditions.
Entonox is a very quick acting painkiller that after a few minutes of inhaling (breathing in) will make you feel relaxed and sleepy whilst relieving your pain. It can also be used for some short uncomfortable procedures such as flexible sigmoidoscopy or colonoscopy as it is safe, quick and has minimal side effects.
The effect of Entonox wears off very rapidly allowing you to fully function within a short time.
Why should I have Entonox for my procedure?
Entonox wear off quickly once you stop breathing it in, so you will not feel any after effects.
One of the most popular advantages of this method of pain relief is that you are in control of how much you have. You are able to drive a car after 30 minutes of its use. You do not need anyone to escort you home and function as normal afterwards.
What are the risk and/or side effects of Entonox?
According to the British Oxygen Company (the company that produce Entonox}, millions of people have used Entonox without a single serious adverse reaction. It has been used successfully on seriously ill patients.
Very occasionally it can cause some minor effects on the cardiovascular and respiratory systems. Entonox can sometimes make you feel sick, give you a dry mouth or can make you feel dizzy. If you have any concerns, please discuss them with a member of staff.
When should I not use Entonox?
Entonox is breathed in by using a mouth piece. The mouth piece is attached to the supply of Entonox. The nurse will show you how to use the Entonox before the procedure begins. You will be encouraged to take 4-6 breaths of Entonox to make sure that you feel its full effects.
You will be holding the mouthpiece yourself. If you breathe too much Entonox and become drowsy you may drop the mouthpiece, this is quite normal. When you are feeling less drowsy, you can hold the mouth piece again and continue to use the Entonox if it is still needed.
What do I need to do after I go home?
You do not have to take any special precautions if you have used Entonox for your procedure, as its effects will have worn off (usually within 30 minutes) by the time you leave the hospital.
Who Can I Contact with Queries and Concerns?
Frimley Park Hospital
For medication queries, please contact the nursing team between 8am –
1pm Monday to Friday:
Endoscopy Unit, Frimley Park Hospital: 0300 613 6045
For appointment queries or to request information leaflets, including diabetic
leaflets, contact the admin team:
Endoscopy booking for Frimley Park Hospital: 0300 613 6647
Frimley - fhft.
Heatherwood Hospital
For medication queries please contact the nursing team between 9am-4pm Monday to Friday
Endoscopy Unit, Heatherwood Hospital: 0300 614 4020
For appointment queries or request information leaflets, including diabetic leaflets, contact the admin team:
Endoscopy booking for Heatherwood Hospital: 0300 614 4009
Wexham Park Hospital
For medication queries please contact the nursing team between 9am-4pm Monday to Friday
Lady Sobell Unit, Wexham Park Hospital: 0300 615 4163
Endoscopy Suite, Wexham Park Hospital: 0300 615 9448
For appointment queries or request information leaflets, including diabetic leaflets, contact the admin team:
Endoscopy booking for Wexham Park Hospital: 0300 615 4157
Contact us
If you have any queries relating to this information, please contact the Endoscopy service.
About this information
Service:
Endoscopy
Reference:
H/028
Approval date:
1 October 2025
Review date:
1 October 2028
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Important note
This page provides general information only. It is developed by clinical staff and is reviewed regularly every 3 years for accuracy. For personal advice about your health, or if you have any concerns, please speak to your doctor.