Description
Fomepizole is the first drug indicated as an antidote for ethylene glycol poisoning (it has also shown promise as a treatment for methanol poisoning). Fomepizole is 4-methyl-1H-pyrazole active as a synthetic alcohol dehydrogenase inhibitor, blocking the formation of toxic ethylene glycol metabolites which are responsible for a severe metabolic acidosis and renal failure. In limited human studies, it reversed the toxicity of potentially lethal doses of ethylene glycol. The main urinary metabolite has been reported to be 4-carboxypyrazole by oxidation of the methyl group. Compared with the current treatment (ethanol), the duration of action is longer and the safety is improved, with no toxic effects reported.
Chemical Properties
clear colourless to yellowish liquid after melting
Originator
Orphan Medical (US)
Uses
Antidote in methanol or ethylene glycol poisoning;Alcohol dehydrogenase inhibitor
Uses
antidote to ethylene glycol or methanol poisoning
Uses
Useful as an antidote in methanol and ethylene glycol poisoning.
Definition
ChEBI: A member of the class of pyrazoles that is 1H-pyrazole substituted by a methyl group at position 4.
Manufacturing Process
Preparation of 4-methylpyrazole
1.0 g (6.67 mmol) of sodium iodide is added to a suspension of 560 g (4.0
mol) of 70% strength sulfuric acid and 62.5 g (1.0 mol) of 80% strength
hydrazine hydrate and, at 125°C, 86.4 g (1.2 mol) of isobutyraldehyde are
pumped under the surface of the suspension over the course of 2 hours using
a metering pump. During and up to 100 min after the addition of
isobutyraldehyde, a total of 175 g of water was distilled out, with the
temperature of the mixture rising to 135°C. The solution is cooled and
adjusted to pH 8.6 with 820 g (5.125 mol) of 25% strength sodium
isobutyraldehyde hydroxide solution and is extracted with isobutanol. The
combined extracts are concentrated to 82 g in a rotary evaporator and then
distilled. The main fraction (boiling point 82°C/7 mbar; 49 g) consists of 82%
4-methylpyrazole. Yield: 49% of theory.
Brand name
Antizol (Jazz).
Therapeutic Function
Antidote
General Description
4-Methylpyrazole inhibits CYP2E1 activity. It also acts as alcohol dehydrogenase inhibitor.
Biochem/physiol Actions
Alcohol dehydrogenase inhibitor.
