Fomepizole
ANTIZOL
What it isA potent alcohol-dehydrogenase inhibitor — the antidote for methanol and ethylene glycol poisoning.
Why this oneIt prevents toxic-metabolite formation predictably without the intoxication and monitoring burden of ethanol therapy.
What limits itIt does not remove toxin or existing acid metabolites, so severe poisoning still requires dialysis and metabolic monitoring; dosing escalates during hemodialysis because the dialyzer removes it.
FDA label
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| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Ethylene glycol or methanol poisoning (antidote; alcohol dehydrogenase inhibitor) | Adults | IV loading dose 15 mg/kg (infuse over 30 min) | Then IV 10 mg/kg q12h x 4 doses, then IV 15 mg/kg q12h until ethylene glycol/methanol undetectable or <20 mg/dL with asymptomatic patient and normal pH | Each dose as slow IV infusion over 30 min; during hemodialysis increase frequency to q4h |
Renal Dialyzable — dose q4h during hemodialysis; consider hemodialysis (in addition to fomepizole) for renal failure, significant/worsening metabolic acidosis, or ethylene glycol/methanol ≥50 mg/dL
Hepatic Undefined
Discontinue when ethylene glycol/methanol undetectable or <20 mg/dL AND patient asymptomatic with normal pH; frequency increases to q4h during hemodialysis
Instructions
- Begin immediately upon suspicion of ethylene glycol/methanol ingestion (anion-gap acidosis, increased osmolar gap, visual disturbance, urinary oxalate crystals) OR documented level >20 mg/dL
- Dilute dose in ≥100 mL 0.9% NaCl or D5W; infuse entire volume over 30 min; diluted solution stable/sterile ≤24 h (no preservatives)
- Do NOT use polycarbonate syringes or polycarbonate-containing needles (incl. filter needles) — fomepizole degrades polycarbonate
- Drug solidifies below 25 C (77 F): liquefy vial under warm water or in hand; solidification does not affect efficacy/safety/stability
- Hemodialysis timing: at HD start give scheduled dose only if ≥6 h since last dose; at HD end give nothing if <1 h since last dose, half dose if 1–3 h, full dose if >3 h; off dialysis resume q12h from last dose
- Monitor ethylene glycol/methanol levels and acid-base balance (anion gap and/or ABG) frequently to guide treatment
Contraindications
- Documented serious hypersensitivity reaction to fomepizole or other pyrazoles
Cautions
- Polycarbonate incompatibility — compromises syringe/needle integrity
- Hemodialysis indicated for high levels (≥50 mg/dL), significant acidosis, or renal failure — adjust dosing schedule accordingly
Adverse reactions
- Headache (14%), nausea (11%), dizziness, drowsiness, bad/metallic taste (6% each)
- Injection-site pain/inflammation, phlebitis; bradycardia, tachycardia, hypotension
- Vomiting, diarrhea, transient transaminitis; eosinophilia; lightheadedness, seizure, agitation, feeling drunk; rash; transient blurred vision; anuria
Pregnancy Undefined
Lactation Undefined
NO BOXED WARNINGS
Classes and tags
Clinical profile
Mechanism of action: Fomepizole ballicule
