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Active substance(s): METHOXYFLURANE

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3mL inhalation vapour, liquid
▼ This medicine is subject to additional monitoring. This will allow
quick identification of new safety information. You can help by
reporting any side effects you may get. See the end of section 4 for how
to report side effects.
Read all of this leaflet carefully
before you start using this
medicine because it contains
important information for you.
• Keep this leaflet. You may
need to read it again.
• If you have any further
questions, ask your healthcare
• If you get any side effects, talk
to your healthcare professional.
This includes any possible side
effects not listed in this leaflet.
See section 4.
What is in this leaflet
1. What Penthrox® is and what it
is used for
2. What you need to know before
you use Penthrox®
3. How to use Penthrox®
4. Possible side effects
5. How to store Penthrox®
6. Contents of the pack and other
1. What Penthrox® is and what it
is used for
Penthrox® contains the active
substance methoxyflurane. It is a
medicine which is used to reduce
pain. It is inhaled through the
custom-built Penthrox® Inhaler.
Penthrox® is intended to reduce
the severity of pain, rather than
stop it completely.
2. What you need to know
before you use Penthrox®
Do not use this medicine if you:
• are allergic to methoxyflurane,
any inhalation anaesthetics or
any of the ingredients listed in
section 6
• have a history or family history
of malignant hyperthermia or
if you or your family have a
history of severe side effects
to methoxyflurane. Malignant
hyperthermia is a condition
where symptoms such as a
very high fever, fast, irregular
heartbeat, muscle spasms
and breathing problems have
occurred after you, or a related
family member, have been
given an anaesthetic
• have previously had
liver damage after using
methoxyflurane or any
inhalation anaesthetics
• have significant kidney
• have a change in the level of
consciousness due to any cause
including head injury, drugs, or
• are suffering from severe
circulatory problems
• have shallow breathing or
difficulty in breathing
If you are not sure whether you
should be given this medicine, talk
to your healthcare professional.
Warnings and precautions
Talk to your healthcare
professional before using this
medicine if you:
• have liver or kidney problems
• have a medical condition which
may cause kidney problems
• are elderly
Do not give this medicine to
Other medicines and Penthrox®
Tell your healthcare professional
if you are taking or have recently
taken any other medicines. In
particular, tell your healthcare
professional if you are taking any
of the following:
• Isoniazid to treat tuberculosis
• Phenobarbital to treat epilepsy
• Rifampicin or other antibiotics
to treat infection
• Medicines, or illegal drugs,
that have a dampening
effect on the nervous system
such as narcotics, pain
killers, sedatives, sleeping
pills, general anaesthetics,
phenothiazines, tranquilisers,
muscle relaxants and sedating
• Antibiotics and other medicines
that may harm the kidney such
as tetracycline, gentamicin,
colistin, polymyxin B,
amphotericin B and contrast
Ask your healthcare professional if
you are unsure.
If you need hospital treatment
requiring general anaesthesia, tell

the doctors treating you that you
have used this medicine.
Taking this medicine with food,
drink and alcohol
Do not drink alcohol whilst taking
this medicine as it may increase
its effect.
You can eat and drink as normal
whilst taking this medicine.
Pregnancy, breast-feeding and
Tell your healthcare professional
before taking this medicine if you
are pregnant, intending to become
pregnant, are breast-feeding or
intending to breast-feed. Your
healthcare professional will discuss
the possible risks and benefits of
being given this medicine.
Driving and using machines
This medicine can affect your
ability to drive or use machines
safely. Make sure these abilities
are not affected before you drive
or operate machinery. Penthrox®
may cause drowsiness or dizziness
in some people.
Butylated hydroxytoluene
This medicine contains a stabiliser
ingredient called butylated
hydroxytoluene (E321). Butylated
hydroxytoluene may cause
local skin reactions (
dermatitis), or irritation to the eyes
and mucous membranes.
3. How to use Penthrox®
Always take this medicine exactly
as your healthcare professional
has told you. Check with your
healthcare professional if you are
not sure.
One or two 3 mL bottles of
Penthrox® can be used per
administration. The maximum
dose is two 3mL bottles per
administration. Do not inhale more
than the maximum dose.
How to use Penthrox®
1. Your healthcare
will prepare
the Penthrox®
Inhaler and
place the wrist
loop over your wrist.
2. Breathe in
through the
of the inhaler
to obtain pain
relief. Your
professional will show you how
if you are unsure. Accustom
yourself to the fruity smell of
the medicine by inhaling gently
for the first few breaths. Breathe
out through the Inhaler. After
the first few breaths breathe
normally through the inhaler.
3. If you need
stronger pain
relief, cover the
dilutor hole on
the transparent
chamber with
charcoal with your finger
during use. Your healthcare
professional will show you
where the hole is.
4. You do not need
to breathe in
and out of the
inhaler all of
the time. Your
healthcare professional will
encourage you to take breaks
from the inhaler as this will
make the pain relief last longer.
5. Continue using your inhaler
until your healthcare
professional tells you to stop,
or when you have inhaled the
maximum recommended dose.
Do not give this medicine to
anyone else, even if they have the
same condition as you.
If you use more Penthrox® than
you should
The healthcare professional giving
the Penthrox® will be experienced
in its use, so it is extremely
unlikely that you will be given
too much. You should not use
more than 2 bottles at one time. If
the maximum dose is exceeded,
Penthrox® may cause damage to
your kidneys. Tell your healthcare
professional immediately if you
think you may have taken too

much of this medicine.
If you have any further questions
on the use of this medicine, ask
your healthcare professional. By
reporting side effects, you can help
provide more information on the
safety of this medicine.

4. Possible Side Effects
Like all medicines, this medicine
can cause side effects, although
not everybody gets them.
Serious side effects
Tell your healthcare professional
immediately if you experience any
of the following:
• Serious allergic reaction,
symptoms include difficulty
breathing and/or swelling of the
• Liver problems, such as loss
of appetite, nausea, vomiting,
jaundice (yellowing of the skin
and/or eyes), dark coloured
urine, pale coloured stools,
pain/ache or sensitivity to touch
in your right stomach area
(below your ribs)
• Kidney problems such as
reduced or excessive urination
or swelling of feet or lower
The above side effects can
be life threatening so tell
your healthcare professional
Other side effects
Common side effects (affects
between 1 and 10 people in 100
• Dizziness
• Drowsiness
• Euphoria
• Difficulty in speaking
• Memory loss
• Anxiety or depression
• Taste disturbance, loss of taste
or dry mouth
• Headache or nausea
• Numbness
• Low blood pressure
• Coughing
• Feeling drunk
• Sweating
Uncommon side effects (affects
between 1 and 10 people in 1000
• Tingling or numbness of the
hands or feet
• Double vision
• Mouth discomfort
• Tiredness
• Feeling abnormal
• Increased appetite
• Shivering
Other side effects (frequency
• Restlessness or agitation
• Feeling of being disconnected
from reality
• Disorientation
• Altered state of consciousness
• Altered mood
• Choking
• Shortness of breath
• Blood pressure fluctuation
• Vomiting
• Blurred vision
Reporting of side effects:
If you get any side effects, talk to
your healthcare professional. This
includes any possible side effects
not listed in this leaflet. You can
also report side effects directly
via the Yellow Card Scheme at

5. How to store Penthrox®
Keep this medicine out of the sight
and reach of children.
Do not use this medicine after the
expiry date. The expiry date refers
to the last day of that month.
This medicinal product does not
require any special temperature
storage conditions and should be
stored in its original container.
Your healthcare professional will
keep Penthrox® combination pack
in a locked cabinet, rather than an
open shelf.
Your healthcare professional will
dispose of any leftover Penthrox®
liquid and the Penthrox® Inhaler
in the appropriate way.
6. Contents of the pack and
other information
What Penthrox® contains
The active substance is
Methoxyflurane. Each 3 mL
sealed bottle contains 99.9%
The other ingredient is Butylated
hydroxytoluene (E321).
What Penthrox® looks like and
contents of the pack
Penthrox® is a clear, almost
colourless volatile liquid, with
a characteristic fruity odour that
becomes a vapour or gas when
used with the Penthrox® Inhaler.
Penthrox® is supplied in the
following presentations:
a) 3 mL bottle with a tear off
tamper-evident seal (packs of
10), or
b) Combination pack with one
3 mL bottle, one Penthrox®
Inhaler and one Activated
Carbon (AC) chamber (packs
of 1 or 10).
Not all pack sizes may be
Marketing Authorisation Holder
and Manufacturer
Marketing Authorisation Holder
Medical Developments UK Ltd.
Causeway House
1 Dane Street,
Bishop’s Stortford
Herts CM23 3BT
United Kingdom
Mawdsley-Brooks & Company Ltd
Unit 22, Quest Park,
Wheatley Hall Road,
Doncaster DN2 4LT
United Kingdom
Galen Limited
Seagoe Industrial Estate
Craigavon BT63 5UA
United Kingdom
This leaflet was last revised in

Information for Healthcare Professionals
The following information is intended for healthcare professionals only:
Instructions on the preparation of the Penthrox® Inhaler and correct
administration are provided in the Figures below:
1. Ensure the
5. Patient
Activated Carbon
exhales into
(AC) Chamber
the Penthrox®
is inserted into
Inhaler. The
the dilutor hole
exhaled vapour
on the top of the Penthrox
passes through the AC
Chamber to adsorb any exhaled
2. Remove the cap of
the bottle by hand.
6. If stronger
Alternatively, use
analgesia is
the base of the
required, patient
Penthrox® Inhaler to
can cover dilutor
loosen the cap with
hole on the AC
a ½ turn. Separate
chamber with finger during
the Inhaler from the bottle and
remove the cap by hand.
7. Patient should
3. Tilt the Penthrox® Inhaler to
be instructed
a 45° angle and
to inhale
pour the total
contents of one
Penthrox® bottle
to achieve adequate analgesia.
into the base of
Continuous inhalation
the Inhaler whilst
will reduce duration of
use. Minimum dose to
4. Place wrist loop
achieve analgesia should be
over patient’s
wrist. Patient
Replace cap
inhales through
onto Penthrox®
the mouthpiece
Place used
of Penthrox Inhaler to obtain
Penthrox® Inhaler
analgesia. First few breaths
and used bottle in
should be gentle and then
sealed plastic bag
breathe normally through
and dispose of responsibly.

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Further information

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