fomepizole (Antizole, 4-methylpyrazole)
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Indications
- suspected or confirmed
* both ethylene glycol poisoning & methanol poisoning are associated with increased anion gap metabolic acidosis
Contraindications
Dosage
- loading dose of 15 mg/kg should be administered, followed by doses of 10 mg/kg every 12 hours for 4 doses, then 15 mg/kg every 12 hours thereafter until ethylene glycol or methanol concentrations are undetectable or have been reduced below 20 mg/dL, and the patient is asymptomatic with normal pH
- all doses should be administered as a slow IV infusion over 30 minutes
Supplied in packages of four vials
Each vial contains 1.5 mL (1 g/mL) of fomepizole
Pharmacokinetics
- volume of distribution 0.6-1.02 L/kg
- therapeutic concentration is from 8.2-24.6 mg/L (100-300 uM)
1/2life varies with dose
- hepatic via cyt P450 system
- primary metabolite is 4-carboxypyrazole (~80-85%)
- fomepizole rapidly induces its own metabolism
- 1-3.5% excreted unchanged in the urine
- metabolites excreted in the urine
- fomepizole is removed by hemodialysis
Monitor
appropriate workup & therapy for metabolic acidosis
Adverse effects
- minor allergic reactions (mild rash, eosinophilia)
- nausea, dizziness, vertigo with overdose
Mechanism of action
- alcohol dehydrogenase inhibitor
- prevents formation of acetaldehyde
More general terms
References
- ↑ Medical Knowledge Self Assessment Program (MKSAP) 16, 18. American College of Physicians, Philadelphia 2012, 2018
- ↑ RxList http://www.rxlist.com/cgi/generic/antizol.htm
- ↑ Brent J. Fomepizole for ethylene glycol and methanol poisoning. N Engl J Med 2009 May 22; 360:2216. PMID: https://www.ncbi.nlm.nih.gov/pubmed/19458366 https://www.nejm.org/doi/full/10.1056/NEJMct0806112