Fomepizol

Fomepizol is a prescription antidote used for poisoning with methanol or ethylene glycol. It acts as a competitive inhibitor of the enzyme alcohol dehydrogenase (ADH), the first step in the metabolism of these toxic alcohols. By blocking ADH, fomepizol prevents the conversion of methanol to formic acid and ethylene glycol to glycolic and oxalic acids, thereby reducing metabolic acidosis, tissue injury, and vision loss.

Fomepizol is indicated for suspected or confirmed methanol or ethylene glycol poisoning, particularly when rapid toxin level measurements are not available or treatment should start before results. It can lessen the need for hemodialysis in some cases, though dialysis remains indicated for severe acidosis, renal failure, or high toxin levels.

Administration and dosing typically involve an intravenous loading dose of 15 mg/kg, followed by 10 mg/kg IV every 12 hours for a minimum of 24 to 72 hours, and continued until methanol and ethylene glycol are undetectable and the patient is clinically stable. Dosing may be adjusted based on clinical response and laboratory data.

Adverse effects are generally mild and may include nausea, headache, dizziness, and injection-site reactions. Hypersensitivity is rare. Fomepizol should be used with caution in hepatic impairment, and patients should be monitored for electrolyte and acid–base disturbances.

Availability and administration are in a hospital setting. Brand-name formulation is marketed as Antizol. In some cases, ethanol therapy may be used as an alternative or adjunct, but coadministration requires careful supervision.