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Methoxyflurane - Inhalation

Pronunciation: meth-OX-ee-FLUR-ane

Common Brand Name(s): Penthrox

Important: How To Use This Information

This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.


This medication may rarely cause kidney or liver damage. To decrease your risk, carefully follow your health care provider's directions for how to use this medication. Tell your doctor right away if you have symptoms of kidney damage (such as change in amount of urine) or liver damage (such as nausea/vomiting that doesn't stop, loss of appetite, stomach/abdominal pain, yellowing eyes/skin, dark urine).


This medication is used for the short-term relief of moderate to severe pain after trauma or during certain medical procedures. It should not be used for relief of pain that keeps coming back or that is ongoing (such as for chronic back pain). It is not clearly known how it works to reduce pain, but it may affect certain natural substances in your body. Methoxyflurane belongs to a class of drugs known as inhalation anesthetics.

This form of methoxyflurane is not used for anesthesia during surgery.

How To Use

Read the Patient Information Leaflet if available from your pharmacist before you start using methoxyflurane and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

A health care professional will help you with how to use the inhaler. Breathe in and out through the mouthpiece of the inhaler as directed by your doctor. Continue breathing in and out through the inhaler until you start to feel pain relief. You may begin to feel pain relief after about 6 to 10 breaths, or within about 5 minutes. If you need stronger pain relief, inhale and use your finger to cover the dilutor hole on the inhaler as directed. You do not need to breathe in and out of the inhaler all of the time. Continue to take breaths through the inhaler from time to time, as needed to control your pain.

The dosage is based on your medical condition and response to treatment. Use the lowest possible dose to get pain relief. Properly stop the medication when so directed.

Though it helps many people, this medication may sometimes cause addiction. This risk may be higher if you have a substance use disorder (such as overuse of or addiction to drugs/alcohol). Use this medication exactly as prescribed to lower the risk of addiction. Ask your doctor or pharmacist for more details.

Tell your doctor if your pain lasts or gets worse.

Side Effects

See also Warning section.

Dizziness, headache, or drowsiness may occur. Mental/mood changes such as trouble with thinking or coordination, feeling "high," or temporary memory problems may also occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

  • rash
  • itching/swelling (especially of the face/tongue/throat)
  • severe dizziness
  • trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.


Before using methoxyflurane, tell your doctor or pharmacist if you are allergic to it; or to other inhaled anesthetics; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

  • breathing problems (such as asthma, chronic obstructive pulmonary disease-COPD)
  • diabetes
  • kidney problems
  • liver problems
  • high or low blood pressure
  • personal or family history of severe allergic reaction to inhaled anesthetic
  • previous use of methoxyflurane
  • substance use disorder (such as overuse of or addiction to drugs/alcohol)

This drug may make you dizzy or drowsy. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is unknown if this medication passes into breast milk. Consult your doctor before breast-feeding.

Drug Interactions

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.


If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Alberta residents can call PADIS (Poison and Drug Information Service) 24 hours a day at 1-800-332-1414. Canada residents can call a provincial poison control center.


Do not share this medication with others.

Missed Dose

Not applicable.


Not applicable. This product is used in a hospital or clinic or doctor's office and will not be stored at home.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

This information does not replace the advice of a doctor. Healthwise, Incorporated, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.