Colonoscopy with PENTHROX® (methoxyflurane) : University College London Hospitals NHS Foundation Trust

What is Penthrox®?

Penthrox® is a pain-relieving medicine, which can be inhaled (breathed in). It contains a type of anaesthetic medicine called methoxyflurane but at a much lower dose than is used as a general anaesthetic (to send people to sleep).

What is Penthrox® used for?

It is licensed for the emergency relief of pain in patients with trauma related pain. At the UCLH endoscopy department Penthrox® is used off-licence as a pain control option for patients undergoing colonoscopy. This is because studies have shown Penthrox® to be as effective as very strong painkillers during colonoscopy, but without the inconvenience of needing to arrange someone to take you home.

How do I use Penthrox®?

Penthrox® is self-administered through a hand-held device called a Penthrox® inhaler, which means you have control of when to use it. There will always be a nurse to supervise you using it. Before the start of your procedure, your nurse will show you how to use the device correctly. It is important to follow their instructions carefully.

Important Safety Information

Penthrox® should be avoided in certain medical conditions or in patients taking certain medications. Prior to your procedure let your endoscopy team know about:

any allergies you have, particularly any previous reactions to anaesthesia (drugs that numb the body or send you to sleep)
any other medications you are taking
any medical conditions you have.

Pregnancy and breastfeeding

Patients who are pregnant or breastfeeding will be offered other pain relief options.

Adverse effects

Like all medications, Penthrox® can cause side effects, although not everyone will experience them. Common side effects include cough, dry mouth, dizziness, drowsiness, amnesia (loss of memory), headache, skin tingling, double vision, skin flushing, sickness.

Rarely, this medicine can cause liver and kidney problems which can occur in the days or weeks after use. Although this is rare, if you experience any of the following seek medical attention:

loss of appetite (loss of appetite can occur immediately after colonoscopy but if this persists for more than 24 hours seek medical attention)
nausea (nausea can occur immediately after colonoscopy but if this persists for more than 24 hours seek medical attention)
vomiting
dark urine
reduced or excessive urination
pale stools
pain or sensitivity to touch in your right stomach area (below your ribs)
swelling of feet or lower legs
jaundice (yellowing of the skin and/or eyes).

Following discharge

If you need hospital treatment requiring general anaesthesia within the next 48 hours, you must tell the doctors treating you that you have used this medicine.
Avoid alcohol for 24 hours after taking this medication.
Penthrox® may cause drowsiness or dizziness in some people. Do not drive or operate machinery if you are feeling drowsy or dizzy.