Adult: Alone or in combination with haemodialysis in patients with known or suspected cases: 15 mg/kg loading dose, followed by 10 mg/kg 12 hourly for 4 doses. Further increase the dose to 15 mg/kg 12 hourly until the ethylene glycol or methanol serum concentrations are reduced to <20 mg/dL, the patient is asymptomatic, and pH is within normal range. All doses are given via slow IV infusion over 30 minutes. Initiate treatment as soon as possible after suspected ingestion or if there's a documented serum ethylene glycol or methanol concentration of >20 mg/dL.
Renal Impairment
Concomitant haemodialysis must be considered in patients with renal failure, significant or worsening metabolic acidosis, or ≥50 mg/dL ethylene glycol or methanol serum concentrations. For patients requiring haemodialysis: Dosing at the start of haemodialysis: Do not give another dose if the last fomepizole dose was given <6 hours ago; administer the next scheduled dose if ≥6 hours have passed since the last fomepizole dose. Dosing during haemodialysis: Increase the dose frequency to 4 hourly; alternatively, 15 mg/kg loading dose via IV infusion over 30-45 minutes, then 1 mg/kg/hour continuous infusion for the whole haemodialysis duration. Dosing upon haemodialysis completion: Do not give a dose at the end of session if the last fomepizole dose was given <1 hour ago; administer 1/2 of the next scheduled dose at the end of haemodialysis if the last fomepizole dose was given 1-3 hours ago; give the next scheduled dose at the end of session if >3 hours have passed since the last fomepizole dose. Maintenance dosing off haemodialysis: Give doses 12 hourly, starting 12 hours from the last dose given. Dosing regimen may vary between countries (refer to detailed local guidelines).
Reconstitution
Concentrated solution for infusion: Withdraw appropriate dose from a vial and dilute with at least 100 mL of NaCl 0.9% inj or dextrose 5% inj.
Contraindications
Known serious hypersensivity reaction to fomepizole or other pyrazoles.
Special Precautions
Not indicated to be given to patients with known isopropanol ingestions since isopropanol toxicity is primarily due to the parent alcohol; inhibiting the isopropanol metabolism may lead to prolonged CNS depression, hypotension or respiratory depression. Not to be administered undiluted or via bolus inj. Renal and hepatic impairment. Pregnancy and lactation.
Adverse Reactions
Significant: Mild hypersensitivity reactions (e.g. eosinophilia, rash); venous irritation and phlebosclerosis (if given via bolus inj at 25 mg/mL concentration). Blood and lymphatic system disorders: Anaemia. Gastrointestinal disorders: Abdominal pain, vomiting. General disorders and admin site conditions: Fever. Nervous system disorders: Headache, agitation. Vascular disorders: Hypotension.
Monitor for serum plasma or urinary concentrations of ethylene glycol or methanol, plasma/urinary osmolality; urinary oxalate crystals; arterial blood gas, anion and osmolar gaps, electrolytes, urinalysis, renal and LFT, CBC, ECG; EEG (in comatose).
Overdosage
Symptoms: Nausea, dizziness and vertigo.
Management: May perform haemodialysis.
Drug Interactions
May decrease the rate of elimination of ethanol and similarly, ethanol may decrease the rate of elimination of fomepizole. May produce reciprocal interactions with CYP450 inducers (e.g. carbamazepine, phenytoin) or CYP450 inhibitors (e.g. cimetidine, ketoconazole).
Action
Description: Mechanism of Action: Fomepizole is a competitive inhibitor of alcohol dehydrogenase, an enzyme that catalyses the oxidation of ethanol to acetaldehyde and the metabolism of ethylene glycol and methanol to their toxic metabolites. Onset: Peak effect: Approx 1.5-2 hours. Pharmacokinetics: Absorption: Readily absorbed from the gastrointestinal tract but usually given via IV. Distribution: Rapidly distributed into total body water. Volume of distribution: 0.6-1.02 L/kg. Plasma protein binding: Negligible. Metabolism: Metabolised in the liver to primary metabolite 4-carboxypyrazole, and other metabolites, 4-hydroxymethylpyrazole and N-glucuronide conjugate; rapidly induces its own metabolism by CYP450 enzymes after multiple doses, resulting to increased rate of elimination. Excretion: Via urine (1-3.5% as unchanged drug and metabolites). Elimination half-life: Varies with dose.
Chemical Structure
Fomepizole Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 3406, Fomepizole. https://pubchem.ncbi.nlm.nih.gov/compound/Fomepizole. Accessed Nov. 24, 2020.
Storage
Intact vial: Store below 25°C. Protect from light. Diluted solution for IV infusion: Store between 2-8°C for not more than 24 hours.
V03AB34 - fomepizole ; Belongs to the class of antidotes. Used in the management of ethylene glycol or methanol poisoning.
References
AFT Pharmaceuticals Ltd. Antizol 1 g/mL Concentrate for Injection data sheet August 2020. Medsafe. http://www.medsafe.govt.nz. Accessed 06/02/2026.Antizol Injection (Paladin Laboratories USA Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 29/10/2020.Brayfield A, Cadart C (eds). Fomepizole. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 06/02/2026.Fomepizole Injection Solution (Zydus Pharmaceuticals USA Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 06/02/2026.Fomepizole Waymade 1 g/mL Concentrate for Solution for Infusion (Waymade PLC). MHRA. https://products.mhra.gov.uk. Accessed 06/02/2026.Fomepizole. UpToDate Lexidrug, AHFS DI (Adult and Pediatric) Online. American Society of Health-System Pharmacists, Inc. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 06/02/2026.Fomepizole. UpToDate Lexidrug, Lexi-Drugs Multinational Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 06/02/2026.
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