Antidote for known or suspected ethylene glycol or methanol ingestion.
- 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.
fomepizole treatment immediately upon suspicion of ethylene
glycol or methanol ingestion based on patient history and/or
unexplanable anion gap metabolic acidosis, osmolar gap, visual
disturbances, or oxalate crystals in the urine.
- Serum ethylene glycol >3.2 mmol/l or methanol
concentration >6.2 mmol/L should be treated.
- 15 mg/kg (mix in minibag and administer over 30 minute infusions
- 10 mg/kg q12h X 4 doses
- then, 15
mg/kg q 12 h
- continue until ethylene glycol < 0.4 mmol/L or serum
methanol levels <0.06 mmol/L
- give the next scheduled dose of fomepizole if more than 6 hours since the last dose
- administer doses every 4 hours
- if less than one hour since the last dose, give the next scheduled dose 12 hours after the last
- if 1 to less than 3 hours since the last dose,give 50% of the next scheduled dose immediately after dialysis completion, then resume normal scheduling
- if 3 hours since last dose, give 100% of the next dose immediately after dialysis completion, then resume normal scheduling.
require increased dosing frequency after 30-40 hours of treatment
due to fomepizole inducing its own hepatic metabolism
Criteria for stopping fomepizole (one of the followin):
- concentration of methanol or ethylene glycol is undetectable
- concentration of methanol is below 3.2 mmol/L or ethylene glycol is below 6.2 mmol/L AND the patient is asymptomatic with a normal pH
Mix dose in a minibag
with a minimum volume of 100 ml dextrose 5 or sodium chloride 0.9% and administer over
at least 30 minutes.
Fomepizole solidifies at temperatures below 25C. Efficacy, safety and stability is not affected. Warm the solidified drug by running the vial under warm water or by holding in the hand.
- Use with caution
in hepatic failure, eliminated extensively by liver. Dose adjustment may be required
reduces the metabolism of ethanol
administration reduces the metabolism of fomepizole by preferential metabolism of ethanol. While ethanol infusion can be used instead of fomepizole to treat methanol or ethylene glycol overdose, these two treatments should not be used together.
in hepatic enzymes
glycol or methanol levels
- blood gases
|Adult Critical Care Protocol:
- May be administered by IV infusion by a nurse in Adult Critical Care