Fomepizole
ANTIZOL
Pronunciation: foe-MEP-i-zoel
What it isPotent alcohol-dehydrogenase inhibitor — the antidote for methanol and ethylene glycol poisoning.
Why this onePrevents toxic-metabolite formation predictably without the intoxication and monitoring burden of ethanol therapy.
What limits itDoes not remove toxin or existing acid metabolites; severe poisoning still requires dialysis and metabolic monitoring. Hemodialysis removes it, requiring higher dosing.
Classes and tags
Clinical profile
Legacy pregnancy categoryC
Defining liabilityTransient CNS effects and infusion-related hypersensitivity
FDA label
Read the full label on DailyMed ↗
NO BOXED WARNINGS
| 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
Available strengths
- inj 1.5 g/1.5 mL
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
Cost
| Strength | #/mo | generic $/unit | CostPlus | |
|---|---|---|---|---|
| 1.5 g/1.5 mL | inj | per unit | not offered |
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Self-check
- Does fomepizole remove existing toxic metabolites?
No. - Why does fomepizole dosing increase during hemodialysis?
The dialyzer removes it.