Methoxyflurane
Pronunciation: (meh-THOK-see-FLOOR-ane).
- Generic name
- Methoxyflurane
- Brand names
- Methox, Methoflur, No currently marketed brands, Penthrox
- Drug class
- Inhalational anesthetic, Analgesic
Availability and supply rules vary by country
Trade names by country:
Australia: · Full directory
What Methoxyflurane is and how it works
Uses, formulations, monitoring, and supply rules can differ by patient, product, and country. Follow the exact local product information and professional advice.
Mechanism of action: how Methoxyflurane works
Methoxyflurane is a volatile fluorinated hydrocarbon that acts as a central nervous system depressant. It modulates neuronal ion channels, particularly enhancing GABAergic transmission and inhibiting excitatory neurotransmission, resulting in analgesia and sedation. At analgesic doses, it provides pain relief without loss of consciousness. (2)
What Methoxyflurane is used for
Pain relief during labor and delivery
Pain relief during labor and delivery (2)
Short-term pain relief for trauma
Short-term pain relief for trauma (2)
Emergency pain relief in pre-hospital settings
Emergency pain relief in pre-hospital settings (2)
Before taking Methoxyflurane
Do not take / not appropriate for
- Contraindicated in patients with known hypersensitivity to methoxyflurane or other halogenated anesthetics, significant renal impairment, history of malignant hyperthermia, or previous adverse hepatic reactions to anesthetics. (Contraindication) (2)
Tell your clinician about
(2)How to take Methoxyflurane
- General Instructions: Methoxyflurane should only be administered under the supervision of a healthcare professional. Patients inhale the vapor through a special device (e.g., Penthrox inhaler) as directed.. Adult Dosing: The usual dose is 3 mL via inhaler, with a maximum of 6 mL in a single day. Do not exceed 15 mL per week, and use on consecutive days is not recommended.. Pediatric Dosing: For children over 5 years, dosing is similar to adults but should be carefully supervised. Not recommended for children under 5 years (the SmPC for the branded product states safety and efficacy in children aged 0-6 years has not been established).. Administration: Inhale slowly and deeply through the mouthpiece. The patient can self-administer, controlling the amount inhaled for pain relief.. When To Stop: Seek medical advice promptly if you experience severe side effects or signs of an allergic reaction; let the clinician supervising your care advise on whether to continue or stop.. Storage: Store below 30°C (86°F), away from direct sunlight and out of reach of children. Do not freeze.
- This page does not provide a dose calculator. Dosing must follow the prescriber, pharmacist, or product label.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (2)
Missed dose
Methoxyflurane is used as needed for pain, so missed doses are not typically an issue. If pain persists, consult your healthcare provider before re-administration.
Overdose
Symptoms of overdose may include severe drowsiness, confusion, respiratory depression, or signs of kidney/liver injury. Seek emergency medical attention immediately if overdose is suspected. (2)
Side effects
Side effects and their urgency vary; report severe, persistent, or concerning symptoms to a healthcare professional.
Nephrotoxicity
Incidence: Reported in the clinician-authored database; frequency not established
Respiratory depression
Incidence: Reported in the clinician-authored database; frequency not established
Malignant hyperthermia
Incidence: Reported in the clinician-authored database; frequency not established
Hepatotoxicity
Incidence: Reported in the clinician-authored database; frequency not established
Hypotension
Incidence: Reported in the clinician-authored database; frequency not established
Nausea
Incidence: Reported in the clinician-authored database; frequency not established
Vomiting
Incidence: Reported in the clinician-authored database; frequency not established
Drowsiness
Incidence: Reported in the clinician-authored database; frequency not established
Serious warnings
US REGULATORY STATUS (ADDED DETAIL) — serious
Symptoms: US REGULATORY STATUS (ADDED DETAIL): methoxyflurane/Penthrox does not have FDA marketing approval in the United States and is legally an unapproved new drug there; it may only be used under an FDA-authorized investigational protocol (e.g., a clinical trial). It is fully approved in the EU (since 2015), Canada (since 2018), Australia, and 40+ other countries.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Risk of kidney and liver toxicity with repeated or high-dose use — serious
Symptoms: Risk of kidney and liver toxicity with repeated or high-dose use. Renal impairment is contraindicated specifically at eGFR below 30 mL/min/1.73m² per SmPC-derived guidance. May cause drowsiness or dizziness; caution with activities requiring alertness. Potential for allergic reactions or malignant hyperthermia. Use only under medical supervision and as directed.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Contraindications recorded in the clinician database — serious
Symptoms: Contraindications recorded in the clinician database: Contraindicated in patients with known hypersensitivity to methoxyflurane or other halogenated anesthetics, significant renal impairment (eGFR <30 mL/min/1.73m²), history of malignant hyperthermia, or previous adverse hepatic reactions to anesthetics. Use with caution in patients with hepatic impairment, elderly, or those at risk of renal dysfunction.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Recorded interactions | Methoxyflurane may interact with other central nervous system depressants (such as opioids, benzodiazepines, or alcohol), increasing the risk of sedation and respiratory depression. It should not be used with other nephrotoxic or hepatotoxic drugs. Inform your healthcare provider about all medications and supplements you are taking. | (1) |
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
Requires a primary-source research pass before this section can be completed. Discuss with the clinician managing the pregnancy. (2)
Breastfeeding
Requires a primary-source research pass before this section can be completed. (2)
Children
Frequency: Not applicable.. Weight Based: Not recommended for pediatric use.. Max Daily Dose: Not applicable.. Max Single Dose: Not applicable.. Age Restrictions: Not recommended under 5 years; the SmPC for the branded product states safety and efficacy in children aged 0-6 years has not been established. (2)
Renal_impairment
Renal: contraindicated at eGFR below 30 mL/min/1.73m². Hepatic: use with caution in hepatic impairment per the clinician database; a graded hepatic-impairment dosing schedule was not established in the sources reviewed for this record. (2)
Hepatic_impairment
Renal: contraindicated at eGFR below 30 mL/min/1.73m². Hepatic: use with caution in hepatic impairment per the clinician database; a graded hepatic-impairment dosing schedule was not established in the sources reviewed for this record. (2)
Monitoring
(2)Storage
Store below 30°C (86°F), away from direct sunlight and out of reach of children. Do not freeze.
Professional information
Clinician-facing context only. This section does not replace current product labeling.
General
Indication: Pain relief during labor and delivery
Dose summary: Inhalation of Methoxyflurane at a concentration of 8% to 10% for analgesia.
Renal context: Contraindicated at eGFR below 30 mL/min/1.73m². (2)
Frequently asked questions
What is methoxyflurane used for?
Methoxyflurane is used for short-term pain relief in emergency situations, minor surgical procedures, and trauma care. It provides rapid, self-controlled pain relief.
How quickly does methoxyflurane work?
Pain relief usually begins within a few breaths and reaches maximum effect within minutes.
Can methoxyflurane be used in children?
Methoxyflurane is approved for use in children over 5 years old under strict medical supervision. It is not recommended for children under 5.
Is methoxyflurane addictive?
Methoxyflurane is not considered addictive when used as directed for short-term pain relief. However, misuse or repeated use can be harmful.
What are the main risks of methoxyflurane?
The main risks are kidney and liver toxicity, especially with repeated or high-dose use. Allergic reactions and drowsiness are also possible.
Can I drive after using methoxyflurane?
You should not drive or operate machinery until you are certain the effects have worn off, as methoxyflurane can cause drowsiness and dizziness.
Is methoxyflurane available in the United States?
No — methoxyflurane (Penthrox) does not have FDA marketing approval in the United States and can only be used there under an authorized clinical trial. It is fully approved and available in Australia, the UK/EU (since 2015), Canada (since 2018), and 40+ other countries.
What happens if I take too much Methoxyflurane?
Taking too much Methoxyflurane can lead to severe central nervous system depression, respiratory arrest, and significant kidney damage. Symptoms may include profound drowsiness, unconsciousness, and difficulty breathing. If an overdose is suspected, immediate medical attention is critical. Seek emergency help without delay.
Can I drink alcohol while taking Methoxyflurane?
No, consuming alcohol while taking Methoxyflurane is strongly discouraged. Both Methoxyflurane and alcohol are central nervous system depressants. Combining them can significantly amplify their sedative effects, leading to excessive drowsiness, respiratory depression, and potentially life-threatening complications. Always avoid alcohol when undergoing treatment with inhalational anesthetics.
Is Methoxyflurane safe during pregnancy?
The safety of Methoxyflurane during pregnancy is not definitively established and it falls into a category where risks cannot be ruled out. It is crucial to consult with your healthcare provider if you are pregnant, planning to become pregnant, or breastfeeding before considering Methoxyflurane. Your doctor will assess the potential benefits against any risks to you and your baby.
What is the mechanism of action of Methoxyflurane?
Methoxyflurane is a volatile fluorinated hydrocarbon that acts as a central nervous system depressant. It modulates neuronal ion channels, particularly enhancing GABAergic transmission and inhibiting excitatory neurotransmission, resulting in analgesia and sedation. At analgesic doses, it provides pain relief without loss of consciousness. (2)
What is the generic name of Methoxyflurane?
The generic name is Methoxyflurane. It is sold under brand names including Methox, Methoflur, No currently marketed brands, Penthrox.
What class of drug is Methoxyflurane?
Methoxyflurane is classed as: Inhalational anesthetic, Analgesic.
References
- Methoxyflurane clinician-authored medicine recordMedGuideGlobal · Global · accessed 2026-08-06 · source 1
- Penthrox (methoxyflurane) inhalation vapour — Summary of Product Characteristics and corroborating guidance from NHS, EMHG, and FDA IND reportingMedicines and Healthcare products Regulatory Agency (UK), European Malignant Hyperthermia Group, NHS Highland, U.S. Food and Drug Administration · United Kingdom, European Union, United States · accessed 2026-08-06 · source 2
Brand names by country
Single-ingredient Methoxyflurane names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.