Fomepizole

Fomepizole is part of the drug class:

• Antidotes

Fomepizole is injected into a vein through an IV. A healthcare provider will give you this injection.

You may be given other medicines and IV fluids as part of your treatment.

Your breathing, blood pressure, oxygen levels, kidney function, and other vital signs will be watched closely while you are receiving fomepizole. Your blood and urine will also need to be tested often during treatment, and your heart function may need to be checked using an electrocardiograph or ECG (sometimes called an EKG).

You will also be watched for any effects of the poisoning, such as problems with vision, breathing, or urination.

Other drugs may interact with fomepizole, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.

Metabolized by mixed-function oxidases (cytochrome P-450 system).b Potent inducer of CYP-mediated drug elimination; induces own metabolism.a b

Drugs Affecting Hepatic Microsomal Enzymes

Inhibitors or inducers of CYP isoenzymes: Potential pharmacokinetic interaction; however, no studies to date.b

Specific Drugs

• Risk of hypersensitivity reactions.1

• Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.1

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, dietary supplements, and/or herbal products, as well as any concomitant illnesses.1

• Importance of informing patients of other important precautionary information.1 (See Cautions.)

• Tell all of your health care providers that you take fomepizole. This includes your doctors, nurses, pharmacists, and dentists.
• Have blood work checked as you have been told by the doctor. Talk with the doctor.
• You will need to have your heart checked before starting this medicine and while taking it. This includes an ECG. Talk with your doctor.
• Tell your doctor if you are pregnant or plan on getting pregnant. You will need to talk about the benefits and risks of using fomepizole while you are pregnant.
• Tell your doctor if you are breast-feeding. You will need to talk about any risks to your baby.

• If you need to store fomepizole at home, talk with your doctor, nurse, or pharmacist about how to store it.

INDICATIONS AND USAGE

Fomepizole Injection is indicated as an antidote for ethylene glycol (such as antifreeze) or methanol poisoning, or for use in suspected ethylene glycol or methanol ingestion, either alone or in combination with hemodialysis (see DOSAGE AND ADMINISTRATION).

(foe ME pi zole)

Disease-related concerns:

• Hepatic impairment: Use with caution in patients with hepatic impairment; metabolized in the liver.

• Renal impairment: Use with caution in patients with renal impairment; fomepizole and its metabolites are excreted in the urine. Hemodialysis should be considered as an adjunct to fomepizole in patients with renal failure, significant acidosis (pH <7.25-7.3), worsening metabolic acidosis, or ethylene glycol or methanol concentrations ≥50 mg/dL.

Special populations:

• Pediatric: Pediatric administration is not FDA approved; however, safe and efficacious use in this patient population for ethylene glycol and methanol intoxication has been reported (Baum, 2000; Benitez, 2000; Boyer, 2001; Brown, 2001; De Brabander, 2005; Detaille, 2004; Fisher, 1998). Consider consultation with a clinical toxicologist or poison control center.

Other warnings/precautions:

• Administration: Should not be given undiluted or by bolus injection.

Ideally, fomepizole plasma concentrations should be monitored; however, fomepizole concentrations are generally not available.

Use these parameters to monitor the response to fomepizole: Plasma (preferred)/urinary ethylene glycol or methanol concentrations, urinary oxalate (ethylene glycol), plasma (preferred)/urinary osmolality, renal/hepatic function, serum electrolytes, arterial blood gases; anion and osmolar gaps, resolution of clinical signs and symptoms of ethylene glycol or methanol intoxication

Applies to fomepizole: intravenous solution

General

The most common adverse events were headache, nausea, dizziness, increased drowsiness, and bad taste/metallic taste.[Ref]

Gastrointestinal

Very common (10% or more): Nausea (11%)
Common (1% to 10%): Abdominal pain, vomiting, diarrhea, dyspepsia, heartburn[Ref]

Nervous system

Very common (10% or more): Headache (14%)
Common (1% to 10%): Dizziness, increased drowsiness, bad taste/metallic taste, lightheadedness, seizure, agitation, feeling drunk, vertigo, nystagmus, anxiety, "felt strange", decreased environmental awareness, abnormal smell, roar in ear[Ref]

Other

Common (1% to 10%): Fever, multiorgan system failure, hangover, speech/visual disturbances[Ref]

Cardiovascular

Common (1% to 10%): Sinus bradycardia/bradycardia, phlebosclerosis, tachycardia, phlebitis, shock, hypotension[Ref]

Hematologic

Common (1% to 10%): Eosinophilia/hypereosinophilia, lymphangitis, disseminated intravascular coagulation, anemia[Ref]

Hepatic

Common (1% to 10%): Transient transaminitis[Ref]

Local

Common (1% to 10%): Pain during injection, inflammation at injection site, application site reaction[Ref]

Genitourinary

Common (1% to 10%): Anuria[Ref]

Respiratory

Common (1% to 10%): Hiccups, pharyngitis[Ref]

Ocular

Common (1% to 10%): Transient blurred vision[Ref]

Dermatologic

Common (1% to 10%): Facial flush, rash[Ref]

Musculoskeletal

Common (1% to 10%): Lumbalgia/backache[Ref]

Metabolic

Common (1% to 10%): Decreased appetite

Some side effects of fomepizole may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.