Fomepizole

Fomepizole is a medication used as an antidote for poisonings caused by methanol and ethylene glycol. It acts as a competitive inhibitor of alcohol dehydrogenase (ADH), the enzyme that metabolizes these toxins to their more dangerous metabolites. By inhibiting ADH, fomepizole prevents the formation of formaldehyde, formic acid, glycolic acid, and other toxic products, reducing risks of metabolic acidosis and organ injury. It also allows the parent compounds to be cleared from the body.

Indications for fomepizole include suspected or confirmed methanol or ethylene glycol poisoning, especially when rapid assessment and treatment are needed. It may be used when ethanol therapy is undesirable or contraindicated. Fomepizole is typically used in conjunction with supportive care and monitoring of acid–base status and toxin levels.

Dosing and administration commonly involve a loading dose of 15 mg/kg given intravenously over about 30 minutes, followed by 10 mg/kg IV every 12 hours for 2 to 3 days. The regimen continues until serum methanol and/or ethylene glycol levels are undetectable and the patient has clinically improved, at which point maintenance dosing can be adjusted or stopped. Doses are adjusted for pediatric patients based on weight. If fomepizole is unavailable, ethanol therapy may be used as an alternative ADH inhibitor.

Adverse effects are generally mild and may include nausea, dizziness, headache, and injection-site reactions. Rare hypersensitivity reactions can occur. Contraindications include hypersensitivity to fomepizole. It is marketed under the brand Antizol and is administered in hospital settings.