Fomepizole: clinical use

Prescribing considerations

• Hospital use should not be delayed solely while awaiting an ethylene glycol assay when poisoning is strongly suspected.
• Fomepizole prevents further toxic metabolite formation but does not reverse established acidosis or remove metabolites.
• Experience is limited in children and older people; hepatic impairment also lacks clinical data.
• Severe poisoning may require supportive treatment and extracorporeal removal.

Contraindications and cautions

• Hypersensitivity to fomepizole, another pyrazole or a formulation component.
• Stop the infusion and treat urgently if major hypersensitivity develops.
• Use caution and closely monitor liver tests in hepatic impairment.
• Avoid routine concurrent ethanol because mutual elimination is reduced.

Monitoring

• Plasma ethylene glycol concentration where available
• Blood gases, acid-base status and electrolytes
• Renal function, urine findings and urinary oxalate crystals
• Hydration and urine output
• Hepatic transaminases and full blood count
• Infusion reactions and major hypersensitivity

Clinical pharmacology

Fomepizole competitively inhibits alcohol dehydrogenase. Elimination is non-linear and saturable; repeated exposure induces its metabolism. It is mainly metabolised before urinary excretion and is dialysable.

Formulation and product differences

• Single-use concentrate requiring dilution with compatible sodium chloride or glucose infusion fluid.
• No listed excipients.
• Solidification at cooler temperatures is reversible by gentle warming.
• Avoid polycarbonate syringes and needles because contact may compromise their integrity.

Solution for infusion

Route: Intravenous

Strengths: 1 g/mL