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Active substance(s): NITROUS OXIDE / OXYGEN

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medicinal gas, compressed
Package leaflet: Information for the user
Oxygen 50%, Nitrous Oxide 50%
Medicinal gas, compressed
Read all of this leaflet carefully before you start
using this medicine.
• Keep this leaflet as you may need to read it
• If you have further questions, ask your
healthcare professional (doctor, midwife, nurse
or pharmacist).
• This medicine has been prescribed for you.
• Do not pass it on to others as it may harm them,
even if their symptoms are the same as yours.
• If any of the side effects become serious, or
if you notice any side effects not listed in this
leaflet, please tell your healthcare professional
This leaflet gives you information about:
1. What is ENTONOX and what is it used for
2. Things to consider before use
3. How to use ENTONOX
4. Possible side effects
5. How to store ENTONOX cylinders
6. Further Information

BOC: living healthcare

ENTONOX is a medicinal gas mixture supplied in
cylinders filled to a high pressure.
ENTONOX is used to relieve pain during:

labour in childbirth
dental treatment
wound cleaning, stitching or dressing
acute trauma such as broken bones
other medical conditions or surgical and
investigative treatments where pain relief is

ENTONOX is only prescribed to you by a healthcare
Ensure that your healthcare professional is aware of
any medical conditions that you may have.

ENTONOX® medicinal gas, compressed package leaflet: Information for the user

Do not use ENTONOX if you have:
• air trapped in a part of the body where it’s
expansion may be dangerous, such as air lodged
in an artery
• a collapsed lung
• decompression sickness (the bends) or if you
have been deep diving within 48 hours
• lung disease or breathing difficulties such as
• injuries to the face and jaw
• head injuries
• a severely bloated stomach
• suspected or known increased pressure on
the brain.
Tell your healthcare professional if you have
recently had any surgery on your eyes or ears
where injections of gas have been used.
Take special care with ENTONOX
If you need to use ENTONOX for more than 24 hours
at a time or more frequently than once every 4
days, your healthcare professional will take routine
blood tests to ensure the ENTONOX has not affected
your blood cell count or the way your body uses
Vitamin B12.
Tell your healthcare professional if you know you
have Vitamin B12 Deficiency.
Inform your healthcare professional if you have
accidentally taken Paraquat (a type of weed killer),
as there is a possibility of toxic effects to the lungs
combined with the high concentration of Oxygen.

Taking other medicines
Please tell your healthcare professional if:
• you are taking Methotrexate for treating arthritis
or cancer. Taking ENTONOX with Methotrexate
may have an affect on your blood cell count
• you are taking medicines to treat anxiety or help
you sleep such as diazepam or lorazepam. These
drugs may increase the effect of ENTONOX
• you have been taking or prescribed Bleomycin
(to treat cancer), Amiodarone (to treat an
irregular heartbeat) or Nitrofurantoin and similar
antibiotics (to treat infection), advise your
healthcare professional before using ENTONOX,
before using ENTONOX, as there is a possibility
of toxic effects to the lungs.
Tell your healthcare professional, if you are taking
or have recently taken any other medicines,
including medicines obtained without a
Pregnancy and breast-feeding
ENTONOX can be used for short term pain relief
during pregnancy.
Ensure that you tell your healthcare professional
that you are pregnant before taking ENTONOX as
they will advise you on the safe use of ENTONOX.
ENTONOX can be used when breast-feeding.
Driving and using machines
­If you have been given ENTONOX on its own for
pain relief, you must wait at least 30 minutes after
use before driving or using any machines.
Ensure that your healthcare professional advises
you whether it is safe for you to drive.

BOC: living healthcare


ENTONOX® medicinal gas, compressed package leaflet: Information for the user

Instructions for use
In a hospital or clinic ENTONOX will be given to you
by a healthcare professional. They will ensure that
your ENTONOX supply is suitable for your use and
that the equipment has been set up correctly.
To breathe your ENTONOX you will either be given a
face mask or mouthpiece. The mask or mouthpiece
is connected to a demand valve system which only
delivers ENTONOX to you as you breathe in.
ENTONOX will begin to take effect immediately
when you start to inhale the gas. The effects
of ENTONOX will quickly wear off once you stop
breathing the gas. You will be able to control how
much ENTONOX you use, depending on the amount
of pain you experience.
If you are using ENTONOX at home you will be
given full training on the use of the cylinder and
equipment when you receive your first supply.
When using your ENTONOX cylinder at home, you
• ensure that the cylinder is stood upright on a
flat surface and supported so that it will not
fall over. Small cylinders may be laid down if
• check the contents gauge on the cylinder or the
regulator before you start to make sure there is
enough gas available for your use
• check that the tubing is correctly fitted to the
gas outlet
• ensure that all equipment is kept free from oil
and grease
• open the cylinder valve slowly
• turn the cylinder valve ‘OFF’ with moderate
force only when the cylinder is not in use

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• if a leak occurs, this will be evident by a hissing
noise. Close the cylinder valve and check the
• close the valve with moderate force only when
the cylinder is empty.
Always use your ENTONOX exactly as your
healthcare professional has shown you. You should
check with your healthcare professional if you are
not sure.
DO NOT SMOKE or have a naked flame near your
ENTONOX gas cylinder. The ENTONOX will make a
flame burn much more violently.
NEVER use oil based moisturising creams with
your cylinder equipment. If using alcohol gels
allow plenty of time for the alcohol gel to dry
before handling your cylinder equipment.
If you use more ENTONOX than you should
If you continue to inhale ENTONOX for too long,
you will become very drowsy and the mask or
mouthpiece will fall away as you relax and hence
there is little risk of an overdose with ENTONOX
when used correctly
If you deliberately, try to use too much ENTONOX
it may eventually result in unconsciousness. If you
become unconscious, your ENTONOX supply should
be turned off and you should be taken to an area
where you can breathe fresh air.
If your breathing has stopped your healthcare
professional will provide the appropriate care,
mouth to mouth resuscitation or use an oxygen
resuscitator if available.

ENTONOX® medicinal gas, compressed package leaflet: Information for the user


If you have any further questions on how this
product is used, ask your healthcare professional.

Reporting of side effects
If you experience any of these side effects, or if
you notice any side effects not listed in this leaflet,
contact your healthcare professional immediately.
You can also report side effects directly to the
Medicines and Healthcare Products Regulatory
Agency (MHRA) via the Yellow Card Scheme www. and to BOC Healthcare. By
reporting side effects you can help provide more
information on the safety of this medicine.



Like all medicines, ENTONOX may cause side
effects, although not everybody will get them.

Expiry Date
Do not use ENTONOX after the expiry date which is
stated on the cylinder batch label.

If you are using ENTONOX at home, have someone
with you to ensure that you have no difficulties
with using the gas. If you take an overdose, you
need to stop breathing the ENTONOX and start
breathing fresh air. If you do not recover, your
helper should call an ambulance and give mouth to
mouth resuscitation if your breathing has stopped.

Common side effects that may occur if you use
• dizziness
• light-headedness
• sickness
• tingling
• disorientation.
Less common side effects that may occur if you use
• problems with the ear due to increased pressure
inside the ear
• tiredness
• bowel enlargement due to trapped gas.
Rare side effects that may occur if you use
• interference with the way your body uses
Vitamin B12, which may affect your blood
cell count
• effects on nerve function including sensations
of numbness and weakness
• difficulty with breathing
• addiction.

BOC: living healthcare

ENTONOX cylinders should be used in strict rotation
so that cylinders with the earliest expiry date are
used first.
Cylinder Storage
Store your ENTONOX cylinders:
• at a temperature of at least 10ºC for at least 24
hours before use. If this is not possible, EA, D
and ED size cylinders should be inverted before
use to ensure the gas is completely mixed
• so that they can not fall over and cause injury
• in clean, well ventilated and dry conditions, not
exposed to extremes of heat or cold
• away from oil, grease and flammable material
in a designated area, where they can be kept
separate from other medical and non-medical
cylinders, with empty and full cylinders kept
• out of sight and reach of children

ENTONOX® medicinal gas, compressed package leaflet: Information for the user

Handling cylinders
Always handle your ENTONOX cylinders with care,
only moving them using an appropriate trolley or
handling device.

What ENTONOX contains
Your ENTONOX cylinder contains 50% Oxygen and
50% Nitrous Oxide.


The colour coding of the shoulder of ENTONOX
cylinders is blue and white. The body is colour
coded white apart from the cylinders marked (*)
in the table above which for a limited period may
have a blue body.
Shoulder of cylinders viewed
from above
Body of cylinder types viewed
from the side

There are no other ingredients.
ENTONOX cylinders
ENTONOX is supplied in the following size cylinders:
Cylinder Size

Cylinder Contents (Litres)

The D, F, G and EW size cylinders need to have a
regulator attached to the cylinder valve before the
gas can be used.
The other cylinders are supplied with an integral
pressure regulator built into the cylinder valve.
Marketing Authorisation Holder and Manufacturer
The Priestley Centre
10 Priestley Road
The Surrey Research Park
Tel 0800 111333

BOC: living healthcare


This leaflet was last approved in

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.