Fomepizole

(BAN, USAN, rINN)
Fomepizole Chemical formula
Synonyms: Fomepitsoli; Fomepizol; Fomépizole; Fomepizolum; 4-Methylpyrazole; 4-MP. 4-Methyl-1H-pyrazole.
Cyrillic synonym: Фомепизол.

💊 Chemical information

Chemical formula: C4H6N2 = 82.10.
CAS — 7554-65-6.
ATC — V03AB34.
ATC Vet — QV03AB34.

💊 Adverse Effects

The most frequent adverse effects associated with fomepizole are headache, nausea, dizziness, drowsiness, and taste disturbances. Abdominal pain, vomiting, diarrhoea, hypotension, tachycardia, hypersensitivity reactions, and raised hepatic enzymes have also been reported.

💊 Pharmacokinetics

Fomepizole is absorbed from the gastrointestinal tract but is usually given intravenously. It is metabolised in the liver, primarily to 4-carboxypyrazole; the metabolites are excreted in the urine, with only a small amount of unchanged drug. After multiple doses, fomepizole induces its own metabolism by the cytochrome P450 enzyme system, significantly increasing the rate of elimination. Fomepizole is removed by dialysis.

💊 Uses and Administration

Fomepizole is a competitive inhibitor of alcohol dehydrogenase. It is used for the treatment of poisoning by ethylene glycol or methyl alcohol, which are converted to toxic metabolites by alcohol dehydrogenase. Fomepizole is given in a loading dose of 15 mg/kg followed by 10 mg/kg every 12 hours for 4 doses; the dose should then be increased to 15 mg/kg every 12 hours until serum concentrations of ethylene glycol or methyl alcohol are less than 20 mg/100 mL. All doses should be given by intravenous infusion over 30 minutes. In patients who also require haemodialysis, doses of fomepizole should be given every 4 hours during haemodialysis sessions. Fomepizole has also been given similarly as the sulfate.
1. Baum CR, et al. Fomepizole treatment of ethylene glycol poisoning in an infant. Pediatrics 2000; 106: 1489–91
2. Brent J, et al. Fomepizole for the treatment of methanol poisoning. N Engl J Med 2001; 344: 424–9
3. Battistella M. Fomepizole as an antidote for ethylene glycol poisoning. Ann Pharmacother 2002; 36: 1085–9
4. Mycyk MB, Leikin JB. Antidote review: fomepizole for methanol poisoning. Am J Ther 2003; 10: 68–70.

💊 Preparations

Proprietary Preparations

Canad.: Antizol; Israel: Antizol; UK: Antizol; USA: Antizol.
Published November 12, 2018.