Fomepizole Intravenous for Adults

Who can administer

May be administered by registered competent doctor or nurse/midwife

Important information

  • Check the brand and strength of the vials

    • There are two brands of different strength vials available: 5mg in 1mL and 1000mg (1g) in 1mL
    • Do not mix brands when preparing a dose
    • GUH generally stocks the 1000mg per mL (1.5g in 1.5mL) strength
  • Doses specified in this monograph are based on the Toxbase database, and differ from manufacturer's advice
  • Poisons Centre must be contacted prior to using this drug
  • See monitoring requirements - next page
  • Unlicensed preparation
  • Very limited stock in GUH - contact pharmacy immediately if a patient is commenced on fomepizole so that further supplies can be organised - see emergency supply contact numbers
  • Available in Emergency Department - antidote press in Resus room

Available preparations

Antizol 1.5g per 1.5mL vial (1,000mg/1mL)

Fomepizole 1.5g per 1.5mL (1,000mg/1mL)

Note- there is also a 5mg/mL strength- but not generally stocked in GUH- see under Important information

Reconstitution

Already in solution

  • If the drug solution has become solid, it should be liquefied by running the vial under warm water (ref 1,2)

Dilute further prior to administration

Infusion fluids

Sodium chloride 0.9% or Glucose 5%

Methods of intravenous administration

Intermittent intravenous infusion (administer using an electronically controlled infusion device)

  • Dilute dose with at least 100mL infusion fluid. (Toxbase suggests 250 to 500ml)
  • Administer over 30 minutes

Dose in adults

IMPORTANT

  • Doses specified in this monograph are based on the Toxbase database, and differ from manufacturer's advice
  • For patients weighing more than 110kg the antidote dose should be calculated using a maximum of 110kg, rather than the patient's actual weight (ref 2)

Loading dose (for patients NOT on haemodialysis)

  • Give 15mg/kg (to a max dose of 1650mg) over 30 minutes
  • The loading dose is still needed in patients who have begun treatment with ethanol as an antidote, who are being switched to fomepizole treatment (ref 2)

Followed by:

  • Doses of 10mg/kg (max dose of 1100mg) over 30 minutes, every twelve hours for four doses, (starting at 12 hours after the loading dose is given (ref 2))
  • After these four doses then give 15mg/kg (max dose of 1650mg) over 30 minutes, every twelve hours thereafter
  • Duration of treatment: Fomepizole should be continued until
    • the ethylene glycol concentration is less than 50 mg/L
    • the methanol concentration is less than 200 mg/L
    • AND
    • acidosis and signs of systemic toxicity have resolved and the osmolal gap is normal
    • Consult specialist centre for advice

Haemodialysis (ref 2)

Consult specialist centre for advice

  • If RRT is initiated more than 6 hours after the last fomepizole dose, or if no fomepizole has been given, administer a loading dose of 15mg/kg (max 1,650mg) over 30 minutes. (another loading dose is not required if six or fewer hours have elapsed since the last dose)
  • For the entire duration of RRT (including time between dialysis sessions) fomepizole may either be given as
    • infusion of 1mg/kg/hour
    • or
    • give 10mg/kg (max 1,100mg) every four hours
  • At the end of RRT
    • if less than 1 hour has passed since the last dose was given, await four hours before restarting twelve-hourly dosing
    • if 1 to 3 hours has passed, give half the dose and restart twelve-hourly dosing in six hours;
    • if more than 3 hours has passed, administer the next twelve-hourly dose

Monitoring

  • Monitor ethylene glycol or methanol concentrations in serum and urine, and the presence of urinary oxalate crystals
  • Monitor LFTs, white blood counts during treatment as transient increases in serum transaminase levels and eosinophilia have been noted with repeated fomepizole dosing
  • Monitor blood pressure and heart rate (ref 1)
  • Monitor for hypersensitivity reactions

Storage

  • Store between 20 and 250C
  • See under reconstitution re temperature changes effects on product

References

Fomepizole (SERB) December 2022 (note this is the 5mg/mL strength) - but is the only SPC available (most information on guide is taken from TOXBASE)

1. Injectable Medicines guide, accessed via Medusa 08/05/2025

2. Toxbase (accessed online 17/04/2025)

Therapeutic classification

Antidote