This page gives you information about having ENTONOX® as pain relief during lower end endoscopic procedures.

What is ENTONOX®?

It is an odourless, colourless gas that has been used for reliable pain relief for over 150 years. It is regularly used in childbirth and other short procedures.

Why is ENTONOX® offered?

If you live alone ENTONOX®. is a good alternative to sedation to help control any discomfort. It can also be used with sedation.


If you have ENTONOX® only, you will not need a responsible adult to stay with you for 24 hours.

How is ENTONOX® given?

ENTONOX® is managed by you, by breathing through a facemask. The facemask will fit over your nose and mouth. This is supervised by a trained health- care professional.

ENTONOX® is safe to use as long as you are able to follow simple instructions.

How long does it take ENTONOX® to work?

ENTONOX® will begin to take effect immediately when you start to inhale the gas.

When you stop breathing in the ENTONOX® the effects of the gas will wear off quickly.

Is it safe to use ENTONOX® while pregnant?

Yes, it is. However, it is best to avoid using it during the first and second trimesters of pregnancy. Your healthcare professional will answer any questions you may have.

Are there any side-effects of using ENTONOX®?

You may get tingling lips and fingertips, feel a little sick or dizzy and it can also give you the ‘giggles’. These effects disappear as the gas eases the pain.

You cannot overdose on this medication.

How soon can I drive after using ENTONOX®?

You should not drive a car or operate any machinery for at least 30 minutes after having ENTONOX®.

Taking other medication with ENTONOX®

Please let the healthcare professional know if you are currently taking any other medication.

A checklist will be completed during your admission to make sure that it is safe for you to use ENTONOX®.

If you have experienced any of the following within the last 12 weeks, ENTONOX® will not be suitable for you:

  • Pneumothorax
  • Air embolism
  • Bowel obstruction
  • Head injury which required you to be in hospital
  • Decompression sickness

ENTONOX® will also not be suitable if:

  • you have emphysema/COPD
  • you have had recent ear/eye surgery
  • you have been scuba diving in in the last 12 weeks

Further information

Printable version of this page

ENTONOX for patient having a Flexible Sigmoidoscopy or Colonoscopy GHPI1663_01_24 Department: Endoscopy Review due: January 2027 PDF, 283.3 KB, 3 pages
Reference number GHPI1663_01_24
Department Endoscopy
Review due January 2027