Alcohol dehydrogenase inhibitor

• Competitively inhibits the enzyme alcohol dehydrogenase. Alcohol dehydrogenase is needed to oxidize ethanol alcohol (found in alcoholic bevridges) to acetaldehyde and to carry out the initial steps in the metabolism of ethylene glycol (found in antifreeze) and methanol (found in windshield washer fluid).
• It is the metabolites of methanol and ethylene glycol that are toxic. By preventing the metabolism of methanol or alcohol, toxicity can be prevented.
• Consider fomepizole treatment immediately upon suspicion of ethylene glycol or methanol ingestion based on patient history and/or anion gap metabolic acidosis, increased osmolar gap, visual disturbances, or oxalate crystals in the urine, or a documented serum ethylene glycol >3.2 mmol/l or methanol concentration >6.2 mmol/L.

• Loading dose 15 mg/kg followed by 10 mg/kg q12h X 4 doses, then 15 mg/kg q 12 h until ethylene glycol < 0.4 mmol/L or serum methanol levels <0.06 mmol/L

Dosing during hemodialysis:

• Before dialysis:  administer next scheduled dose if >6 hours since the last dose.
• During dialysis: administer doses every 4 hours.
• Postdialysis: if time since last dose is <1 hour, then give the next scheduled dose 12 hours from the last dose administered, and then follow the normal dosing schedule

• May require increased dosing frequency after 30-40 hours of treatment due to fomepizole inducing its own hepatic metabolism

• Use with caution in hepatic failure.

• Fomepizole reduces the metabolism of ethanol.
• Ethanol administration reduces the metabolism of fomepizole. While ethanol infusion can be used instead of fomepizole to treat methanol or ethylene glycol overdose, these two treatments should not be used together.

• Headache
• Nausea
• Dizziness
• Increased drowsiness
• Bad taste/metallic taste
• Increase in hepatic enzymes

• Ethylene glycol or methanol levels
• Response to ethylene glycol or methanol intoxication parameters

• May be administered by a nurse.