4-Methylpyrazole

Absorption

Rapid and complete

Toxicity

Headache, nausea, dizziness

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.

Description

Fomepizole is a competitive inhibitor of alcohol dehydrogenase, the enzyme that catalyzes metabolism of ethylene glycol and methanol to toxic metabolites. At 10 μM in monkeys, it can prevent the formation of toxic alcohol metabolites that generate metabolic acidosis. This compound is typically used as an antidote for ethylene glycol or methanol poisoning.

Chemical properties

clear colourless to yellowish liquid after melting

Originator

Orphan Medical (US)

The Uses of 4-Methylpyrazole

Useful as an antidote in methanol and ethylene glycol poisoning.

The Uses of 4-Methylpyrazole

Antidote in methanol or ethylene glycol poisoning;Alcohol dehydrogenase inhibitor

The Uses of 4-Methylpyrazole

antidote to ethylene glycol or methanol poisoning

The Uses of 4-Methylpyrazole

Fomepizole (4-Methylpyrazole) can be used as:

• A reactant to prepare 4-methyl-1-phenyl-1H-pyrazole by reacting with bromobenzene via N-arylation using a copper catalyst.
• A starting material for the synthesis of 4-methyl-3(5)-nitropyrazole by nitration.
• A ligand in the preparation of gallium(III) complex of 4-methylpyrazole as potential antitumor and antiviral agent.

Indications

Antizol is indicated as an antidote for ethylene glycol (such as antifreeze) or methanol poisoning, or for use in suspected ethylene glycol or methanol ingestion, either alone or in combination with hemodialysis

Background

Fomepizole is used as an antidote in confirmed or suspected methanol or ethylene glycol poisoning. Fomepizole is a competitive inhibitor of alcohol dehydrogenase, the enzyme that catalyzes the initial steps in the metabolism of ethylene glycol and methanol to their toxic metabolites.

What are the applications of Application

Fomepizole is an alcohol dehydrogenase inhibitor

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.

Pharmacokinetics

Fomepizole is a competitive inhibitor of alcohol dehydrogenase, the enzyme that catalyzes the initial steps in the metabolism of ethylene glycol and methanol to their toxic metabolites. Ethylene glycol is first metabolized to glycoaldehyde which then undergoes further oxidation to glycolate, glyoxylate, and oxalate. Glycolate and oxalate are primarily responsible for metabolic acidosis and renal damage seen in ethylene glycol toxicity. {01}{03} Methanol is first metabolized to formaldehyde and then undergoes subsequent oxidation via formaldehyde dehydrogenase to become formic acid. It is formic acid that is primarily responsible for the metabolic acidosis and visual disturbances that are associated with methanol poisoning.

Metabolism

Primarily hepatic. the primary metabolite is 4-carboxypyrazole (approximately 80 to 85% of an administered dose). Minor metabolites include 4-hydroxymethylpyrazole and the N -glucuronide conjugates of 4-carboxypyrazole and 4-hydroxymethylpyrazole.