Fomepizole Dosage

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Usual Adult Dose for:

Usual Pediatric Dose for:

Additional dosage information:

Usual Adult Dose for Methanol Poisoning

Patients not requiring hemodialysis:
Initial dose: 15 mg/kg IV followed by 4 doses of 10 mg/kg IV every 12 hours

Maintenance dose: 15 mg/kg IV every 12 hours thereafter until levels of ethylene glycol or methanol are reduced below 20 mg/dL, and the patient is asymptomatic with normal pH

All doses should be administered as a slow intravenous infusion over 30 minutes.

Usual Adult Dose for Ethylene Glycol Poisoning

Patients not requiring hemodialysis:
Initial dose: 15 mg/kg IV followed by 4 doses of 10 mg/kg IV every 12 hours

Maintenance dose: 15 mg/kg IV every 12 hours thereafter until levels of ethylene glycol or methanol are reduced below 20 mg/dL, and the patient is asymptomatic with normal pH

All doses should be administered as a slow intravenous infusion over 30 minutes.

Usual Pediatric Dose for Methanol Poisoning

Children and adolescents not requiring hemodialysis:
Initial dose: 15 mg/kg IV followed by 4 doses of 10 mg/kg IV every 12 hours

Maintenance dose: 15 mg/kg IV every 12 hours thereafter until levels of ethylene glycol or methanol are reduced below 20 mg/dL, and the patient is asymptomatic with normal pH

All doses should be administered as a slow intravenous infusion over 30 minutes.

Not FDA approved; however, safe and effective use in pediatric patients has been reported.

Usual Pediatric Dose for Ethylene Glycol Poisoning

Children and adolescents not requiring hemodialysis:
Initial dose: 15 mg/kg IV followed by 4 doses of 10 mg/kg IV every 12 hours

Maintenance dose: 15 mg/kg IV every 12 hours thereafter until levels of ethylene glycol or methanol are reduced below 20 mg/dL, and the patient is asymptomatic with normal pH

All doses should be administered as a slow intravenous infusion over 30 minutes.

Not FDA approved; however, safe and effective use in pediatric patients has been reported.

Renal Dose Adjustments

Data not available

Liver Dose Adjustments

Data not available

Precautions

Fomepizole should not be administered to patients with a documented serious hypersensitivity reaction to fomepizole or other pyrazoles. Patients should be monitored for signs of allergic reactions. Minor allergic reactions have been reported including mild rash and eosinophilia.

Fomepizole should not be administered undiluted or by bolus injection. Venous irritation and phlebosclerosis have been reported when bolus doses were administered at a concentration of 25 mg/mL.

Hepatic enzymes and white blood cell counts should be monitored, as transient increases in serum transaminase concentrations and eosinophilia have been reported with repeated fomepizole dosing.

The safety and effectiveness of fomepizole in pediatric and geriatric patients have not been established.

Dialysis

Patients requiring hemodialysis:
Dose at the beginning of hemodialysis:
Less than 6 hours since last fomepizole dose: Do not administer dose.
6 hours or more since last fomepizole dose: Administer next scheduled dose.

Dose during hemodialysis: Administer every 4 hours or as a continuous infusion 1 to 1.5 mg/kg/hour.

Dose at the time hemodialysis is completed:
Less than 1 hour between last dose and the end of hemodialysis: Do not administer dose at the end of hemodialysis.
1 to 3 hours between last dose and the end of hemodialysis: Administer half of next scheduled dose.
Greater than 3 hours between last dose and end of hemodialysis: Administer next scheduled dose.

Maintenance dose off hemodialysis: Give next scheduled dose 12 hours from last dose administered.

Other Comments

Fomepizole should be started immediately upon suspicion of poisoning based on patient history and/or anion gap metabolic acidosis, increased osmolar gap, visual disturbances, or oxalate crystals in the urine, or if the patient has serum ethylene glycol or methanol concentration greater than 20 mg/dL.

Hemodialysis should also be considered in addition to fomepizole if the patient has renal failure, significant or worsening metabolic acidosis, or a measured ethylene glycol or methanol concentration of 50 mg/dL or greater.

In addition to antidote treatment, patients should also be managed for metabolic acidosis, acute renal failure (ethylene glycol intoxication), respiratory distress syndrome, visual disturbances (methanol intoxication), and hypocalcemia. Support therapies may include fluids, sodium bicarbonate, potassium and calcium supplementation, and oxygen.

Blood gases, pH, electrocardiography, electrolytes, BUN, creatinine, urinalysis, and other laboratory tests should be monitored frequently to guide fomepizole treatment. Patients with ethylene glycol intoxication should have serum and urinary ethylene glycol concentrations monitored, as well as the presence of urinary oxalate crystals. Likewise, patients with methanol intoxication should have serum methanol levels monitored. Comatose patients may also require electroencephalography.

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