Methoxyflurane (Penthrox®) - EMed

Home » What Is In The Green Whistle » Methoxyflurane (Penthrox®) - EMed

Maybe your like

Methoxyflurane (Penthrox®) Background Indications Contraindications Dosage Administration Links

Penthrox® - "Green whistle"

Penthrox - green whistle
  • Methoxyflurane (C3H4Cl2F2O) is a volatile fluorinated hydrocarbon
  • Colourless liquid analgesic with a fruity odour
  • Highly lipophilic and rapidly absorbed via inhalation
  • Potentiated through GABA receptors & two-pore K+ channels
  • Metabolised in liver (CYP450 isozymes):
    • Metabolites include: Fluoride,  oxalic acid,di-fluoromethoxyacetic acid, di-chloroacetic acid
    • 60% excreted in urine: fluorine, fluoride & oxalic acid
    • Remainder is exhaled
    • Metabolites can cause renal damage at high concentrations

Indications

  • Emergency patient controlled analgesia for conscious adults with trauma associated moderate/severe pain
  • Max 2 x 3 mL doses in 24hrs and
  • Max 15ml / week (potentially nephrotoxic)

Dosage

  • Single dose of Penthrox = 3 mLs (1 bottle)
  • 1 hour of analgesia if used intermittently
  • Max. dose not to exceed 6 mLs (2 bottles)

Contraindications - CHECK

C - Clinically significant cardiac or respiratory disease

H - Hypersensitivity to methoxyflurane (or any fluorinated anaesthetic)

E - Established or Hx malignant hypertherima

C- Consciousness altered

K - Kidney (eGFR < 45mL/min or on nephrotoxic antibiotics) or liver disease

Administration

Step 1
Ensure the Activated Carbon (AC) Chamber is inserted into the dilutor hole on the top of the inhaler
Step 2
Remove the cap of the bottle by hand. Alternatively, use the base of the inhaler to loosen the cap with a ½ turn. Separate the inhaler from the bottle and remove the cap by hand.
Step 3
Tilt the inhaler to a 45° angle and pour the total contents of one bottle into the base of the inhaler whilst rotating
Step 4
Place wrist loop over patient’s wrist. Patient inhales through the mouthpiece of the inhaler to obtain analgesia. First few breaths should be gentle and then breathe normally through Inhaler.
Step 5
Patient exhales into the inhaler (to protect you). The exhaled vapour passes through the AC Chamber to adsorb any exhaled methoxyflurane.
Step 6
If stronger analgesia is required, patient can cover dilutor hole on the AC Chamber with finger during use.
Step 7
Patient should be instructed to inhale intermittently to achieve adequate analgesia. Continuous inhalation will reduce duration of use. Minimum dose to achieve analgesia should be administered.
Step 8
Replace cap onto bottle. Place used inhaler and used bottle in sealed plastic bag and dispose of responsibly in a designated bin or suitable waste container.

Links

  • HPRA administration guideline

Content by Prof Conor Deasy, Dr Íomhar O' Sullivan. Last review Dr ÍOS 18/05/25.

Tag » What Is In The Green Whistle