Fomepizole Intravenous for Adults

Who can administer

May be administered by registered competent doctor or nurse/midwife

Important information

  • 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

Fomepizole 1.5g per 1.5mL (SteriMax)

Reconstitution

Already in solution

  • The drug solidifies at temperatures less than 250C. If the drug solution has become solid, it should be liquefied by running the vial under warm water or by holding in the hand
  • Solidification does not affect the safety, efficacy or stability of the drug

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 1)

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 1)

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 1))
  • After these four doses then give 15mg/kg (max dose of 1650mg) over 30 minutes, every twelve hours thereafter until ethylene glycol or methanol levels are undetectable or have been reduced below 50mg/dL (ref 1) (below 20mg/dL according to manufacturer) AND acidosis and signs of systemic toxicity have resolved. Consult specialist centre for advice

Haemodialysis (ref 1)

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

Storage

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

References

Antizol;Package insert 2nd May 2017

Fomepizole (SteriMax) June 14th 2018

(1) Toxbase (accessed online 29/09/21)

Therapeutic classification

Antidote