Products
Methoxyflurane has been approved in many countries since 2018 as a liquid to produce a vapor for inhalation (Penthrox, inhaler). In Australia, the drug has been used since the early 1970s. The active ingredient was originally launched in the 1960s as an anesthetic, but is no longer used as such.
Structure and properties
Methoxyflurane (C3H4Cl2F2O, Mr = 164.96 g/mol) exists as a clear, almost colorless, volatile liquid with a sweet and fruity odor. It is a lipophilic chlorinated and fluorinated ether.
Effects
Methoxyflurane (ATC N02BG09) has analgesic (pain-relieving), sedative, anxiolytic, and, at higher doses, anesthetic properties. It enters the lungs as a vapor, where it passes into the bloodstream and rapidly induces its effects in the central nervous system. Pain relief occurs after about 6 to 10 inhalations. Continuous inhalation can provide analgesia for a period of up to 30 minutes.
Indications
For emergency treatment of moderate to severe trauma-related pain in conscious adult patients. In other countries, methoxyflurane is also approved for brief procedures such as biopsies.
Dosage
According to the SmPC. Methoxyflurane is self-administered by patients using an inhaler under the guidance and supervision of a healthcare professional. Dosage must be kept as low as possible because of its renal toxic properties.
Abuse
Methoxyflurane can be abused as an intoxicant because of its euphoric and depressant properties.
Contraindications
Refer to the drug label for complete precautions.
Interactions
Methoxyflurane is a substrate of CYP450 isozymes, particularly CYP2E1 and, to some extent, CYP2A6. Corresponding interactions may occur. Central depressant drugs and alcohol may potentiate adverse effects. Other interactions have been described with barbiturates, beta blockers, calcium channel blockers, and nephrotoxic drugs.
Adverse effects
The most common adverse effect is dizziness. Other common adverse effects include:
- Euphoria, amnesia, impaired speech.
- Taste disturbances, dry mouth, nausea.
- Headache, fatigue, drowsiness, drowsiness.
- Low blood pressure
- Cough
Methoxyflurane has nephrotoxic properties and may impair renal function in a dose-dependent manner. Therefore, it is no longer used as an anesthetic. The appropriate precautions, interactions and maximum single, daily and weekly doses must be observed. For this reason, methoxyflurane is also not suitable for repeated treatment, e.g., for chronic pain. However, low-dose methoxyflurane has few renal adverse effects according to the literature.
