Information Sheet
Penthrox “green whistle”
Information sheet: Penthrox “green whistle”
PDF version: Penthrox “green whistle” (ENG, PDF).
Ref code: 1816-MSIAU
Penthrox® (methoxyflurane) is a pain-relief medicine that you breathe in through a small handheld device, called the ‘green whistle’.
It can help reduce pain during procedures such as IUD insertion, but it may not take all the pain away.
A nurse or doctor will be with you while you use it.
How do I use it?
You hold the “green whistle” and you decide when to use it.
To use the inhaler:
- Place the mouthpiece between your teeth
- Close your lips around the mouthpiece
- Breathe normally through the mouthpiece
Most people start to feel the effects after 6 to 10 breaths. Once it begins to work, you can use it as needed. Pain relief can continue for several minutes after you stop using it.
The medicine has a fruity smell and taste. Most people get used to this after a few breaths.
Is Penthrox right for me?
Penthrox may not be suitable for everyone.
Tell your nurse or doctor if:
- You have an allergy to methoxyflurane orany inhaled anaesthetics.
- You have had liver problems afterusing methoxyflurane or other inhaledanaesthetics.
- You or a family menber has had malignanthyperthermia (a rare life-threateningreaction to anaesthetics).
- You have severe liver or kidney problems.
What will I feel while using it?
Most people feel more comfortable during their procedure when using Penthrox.
- You may also notice:
- Feeling dizzy or light-headed
- Feeling sleepy
- Headache
- Nausea (feeling sick) or vomiting
- Cough
- Flushing or tingling skin
These are usually mild and short-lasting. Tell your nurse or doctor straight away if you feel unwell or are worried about any symptoms.
After your procedure
The effects of Penthrox wear off quickly, and most people can leave the clinic soon after their procedure.
If you are driving, you will need to stay in the clinic for 30 minutes after your procedure so our staff can make sure you have recovered.
Do not drive a vehicle, operate machinery, or do anything that needs concentration or quick reactions until you feel fully recovered.
If possible, consider arranging for someone to go home with you. If you have persistent dizziness, severe nausea or vomiting, difficulty breathing, rash, or any other concerning symptoms after leaving the clinic, contact us on 1300 888 022, or seek medical advice.
This page last edited: October 2026