Overview
DESCRIPTION Fomepizole Injection is intended for intravenous use. Fomepizole Injection is a competitive inhibitor of alcohol dehydrogenase. The chemical name of fomepizole is 4-methylpyrazole. It has the molecular formula C 4 H 6 N 2 and a molecular weight of 82.1. The structural formula is: It is a clear to yellow liquid at room temperature.
Mechanism of Action
CLINICAL PHARMACOLOGY Mechanism of Action: Fomepizole is a competitive inhibitor of alcohol dehydrogenase. Alcohol dehydrogenase catalyzes the oxidation of ethanol to acetaldehyde. Alcohol dehydrogenase also catalyzes the initial steps in the metabolism of ethylene glycol and methanol to their toxic metabolites. Ethylene glycol, the main component of most antifreezes and coolants, is metabolized to glycolaldehyde, which undergoes subsequent sequential oxidations to yield glycolate, glyoxylate, and oxalate. Glycolate and oxalate are the metabolic by products primarily responsible for the metabolic acidosis and renal damage seen in ethylene glycol toxicosis. The lethal dose of ethylene glycol in humans is approximately 1.4 mL/kg.
Indications
- INDICATIONS AND USAGE Fomepizole injection 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 (see DOSAGE AND ADMINISTRATION ).
Common Doses
- 50 mg
- 20 mg
- 15 mg
- 10 mg
Dosage
DOSAGE AND ADMINISTRATION Do not use polycarbonate syringes or polycarbonate-containing needles (including polycarbonate filter needles) when diluting or administering fomepizole injection. Fomepizole can interact with polycarbonate, compromising the integrity of the syringe and/or needle component containing polycarbonate. Treatment Guidelines: If ethylene glycol or methanol poisoning is left untreated, the natural progression of the poisoning leads to accumulation of toxic metabolites, including glycolic and oxalic acids (ethylene glycol intoxication) and formic acid (methanol intoxication).
Contraindications
- CONTRAINDICATIONS Fomepizole should not be administered to patients with a documented serious hypersensitivity reaction to fomepizole or other pyrazoles.
Side Effects
- ADVERSE REACTIONS The most frequent adverse events reported as drug-related or unknown relationship to study drug in the 78 patients and 63 normal volunteers who received fomepizole injection were headache (14%), nausea (11%), and dizziness, increased drowsiness, and bad taste/metallic taste (6% each). All other adverse events in this population were reported in approximately 3% or fewer of those receiving fomepizole injection and were as follows: Body as a Whole: Abdominal pain, fever, multiorgan system failure, pain during fomepizole injection, inflammation at injection site,...
Interactions
- Drug Interactions: Oral doses of fomepizole (10 to 20 mg/kg), via alcohol dehydrogenase inhibition, significantly reduced the rate of elimination of ethanol (by approximately 40%) given to healthy volunteers in moderate doses. Similarly, ethanol decreased the rate of elimination of fomepizole (by approximately 50%) by the same mechanism. Reciprocal interactions may occur with concomitant use of fomepizole and drugs that increase or inhibit the cytochrome P450 system (e.g., phenytoin, carbamazepine, cimetidine, ketoconazole), though this has not been studied.