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Methoxyflurane

Classification

Inhaled anesthetic

Indications

EMR: Moderate to severe pain associated with trauma or interventional medical procedures

Contraindications

Pediatrics < 18 years of age
Inadequate patient understanding or lack of cooperation
Decreased level of consciousness
History of clinically significant renal impairment
History of liver dysfunction following previous exposure to halogenated anesthetics
Current use of tetracycline antibiotics
Personal or familial history of malignant hyperthermia
Muscular dystrophy
Pregnancy, intended pregnancy, or current breast-feeding

Adult dosages

EMR: Moderate to severe pain associated with trauma or interventional medical procedures

3 mL via inhaler; may repeat after 20 minutes; maximum total volume 6 mL

Patients must self-administer as needed under direct paramedic supervision

Pediatric Considerations And Dosing

Not authorized for patients under 18 years of age

Mechanism Of Action

The specific mechanism of action of halogenated anesthetics is not well understood. Methoxyflurane is the only volatile anesthetic agent with significant analgesic properties at low, sub-anesthetic doses.

Pharmocokinetics

Inhaled:

Onset: 1-3 minutes / 8-10 breaths
Duration: approximately 25 minutes per 3 mL / 3-5 minutes once discontinued

Adverse Effects

Altered level of consciousness (mainly drowsiness)
Cough
Hypotension and bradycardia (rare)

Overdose

Doses of methoxyflurane that exceed therapeutic doses have been shown to produce serious, irreversible nephrotoxicity. Follow dosing guidelines and do not exceed recommended amounts.

Although unlikely in the out-of-hospital setting, patients should not receive more than 6 mL in any 48 hour period and no more than 15 mL over 1 week.

Warning And Precautions

Methoxyflurane carries unique risks for paramedics, particularly with chronic exposure. As such, limit administration of methoxyflurane inside ambulances to a single 3 mL dose; where possible, ensure adequate ventilation through the use of exhaust fans, and set ambulance heater or AC to any position but "Max AC" (as this is a recirculating mode).

Ensure that patients exhale through the carbon filter.

No single employee should administer more than 3 doses of methoxyflurane per shift.