Fomepizole
Fomepizole is an antidote used to treat or prevent serious poisoning from ethylene glycol (antifreeze) or methanol (found in windshield wiper fluid).
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 7 clinical label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
📖 Fomepizole: Patient Information Guide
A plain-language walkthrough of Fomepizole — what it treats, how it works, how it’s taken, side effects, warnings and interactions. Tap any section to expand it.
🎯What it's used for▾
Fomepizole is an antidote used in emergency and hospital settings. It is FDA-approved for the following:
- Treatment of confirmed ethylene glycol (antifreeze or coolant) poisoning — given as an injection
- Treatment of confirmed methanol (windshield wiper fluid) poisoning — given as an injection
- Treatment of suspected ethylene glycol or methanol poisoning, even before blood levels are confirmed — given as an injection
- Use alone or in combination with hemodialysis (blood-filtering dialysis) when poisoning is severe
⚙️How it works▾
Fomepizole works by blocking an enzyme called alcohol dehydrogenase. Normally, this enzyme converts ethylene glycol into toxic acids (like glycolate and oxalate) and converts methanol into formic acid. These byproducts are what cause the serious harm — kidney damage, severe acid buildup in the blood, and blindness. By blocking this enzyme early, fomepizole prevents those toxic substances from forming, giving the body time to safely eliminate the original poison.
With repeated doses over 30 to 40 hours, fomepizole actually speeds up its own removal from the body by activating a liver enzyme system called cytochrome P450. This means dosing adjustments may be needed during longer treatment courses.
💊How it's taken▾
Fomepizole injection is given intravenously (into a vein) by a healthcare professional — always in a hospital or emergency care setting. Each dose is infused slowly over 30 minutes. Treatment is typically started immediately when poisoning is suspected and continues until blood levels of the poison have dropped to a safe range and the patient has returned to a normal blood pH.
- During hemodialysis, doses are given more frequently — the care team adjusts timing around each dialysis session
- The frequency and duration of treatment are entirely managed by the medical team based on ongoing blood monitoring
🤒Side effects — in detail▾
The most commonly reported side effects of fomepizole injection include:
- Headache
- Nausea
- Dizziness or lightheadedness
- Increased drowsiness
- Bad or metallic taste in the mouth
- Pain or irritation at the injection site
- Vomiting
- Fever
More serious reactions — including seizures, vision disturbances, abnormal heart rhythms, severe low blood pressure, or signs of an allergic reaction such as rash — should be reported to medical staff right away.
⚠️Warnings & precautions▾
- Allergy: Fomepizole injection must not be given to anyone with a known serious allergic reaction to fomepizole or to other pyrazole compounds.
- Hemodialysis adjustment: Fomepizole is removed by dialysis. If you are on hemodialysis, the dosing schedule must be carefully adjusted so that therapeutic levels are maintained throughout dialysis.
- Alcohol interaction: Fomepizole significantly slows the body's ability to process alcohol, and alcohol slows the clearance of fomepizole. Both can accumulate to higher levels if taken together.
- Kidney and liver disease: Fomepizole's breakdown products are cleared through the kidneys, and the drug itself is processed by the liver. Patients with kidney or liver problems may need extra monitoring.
- Enzyme induction: After about 30 to 40 hours of dosing, fomepizole speeds up its own elimination through a liver enzyme system. This can affect how well the drug works and may require dose timing changes.
🔀What it interacts with▾
Fomepizole interacts with several substances through shared enzyme pathways. Tell your care team about everything you take:
- Ethanol (alcohol): Fomepizole slows alcohol clearance by about 40%, and alcohol slows fomepizole clearance by about 50% — both can reach unexpectedly high levels together
- Phenytoin (Dilantin) and carbamazepine (Tegretol): These seizure medications may interact via the cytochrome P450 liver enzyme system
- Cimetidine (Tagamet): This acid-blocking medication may interact through the same cytochrome P450 pathway
- Ketoconazole (antifungal): May also interact through cytochrome P450 enzymes
This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.
📋Before taking it▾
- Do not receive fomepizole if you have ever had a serious allergic reaction to fomepizole or any other pyrazole compound
- Tell your care team if you have kidney disease — fomepizole's breakdown products are excreted through the kidneys
- Tell your care team if you have liver disease — fomepizole is metabolized in the liver
- Older adults: pharmacokinetics have not been fully studied in this population; extra monitoring may be appropriate
- Children: pharmacokinetics have not been fully studied in pediatric patients
- Share a complete list of all medications with your treating team, especially seizure medications, antifungals, and acid-blocking drugs
🚑If you take too much▾
In studies, healthy volunteers who received doses much higher than the recommended amount (3 to 6 times higher) experienced nausea, dizziness, and vertigo. These effects were dose-related and generally short-lived, though they lasted up to 30 hours in one individual. Because fomepizole can be removed by hemodialysis, dialysis may be used to help treat an overdose if needed.
📡Pharmacodynamics — effects in the body▾
Fomepizole blocks alcohol dehydrogenase, the enzyme responsible for converting ethylene glycol and methanol into their harmful toxic byproducts. By inhibiting this enzyme, fomepizole prevents the formation of the acids (glycolate, oxalate, and formic acid) that cause metabolic acidosis (dangerous acid buildup in the blood), kidney damage, and visual disturbances — including potential blindness. In animal studies, fomepizole given within hours of ethylene glycol ingestion prevented severe kidney damage and corrected acid-base imbalance.
🔬Pharmacokinetics — how your body processes it▾
After intravenous infusion, fomepizole distributes quickly throughout body water, reaching tissues broadly. The drug is primarily broken down by the liver — less than 3.5% is excreted unchanged in the urine. Its main breakdown product is 4-carboxypyrazole, which accounts for about 80 to 85% of the administered dose and is cleared through the kidneys. With repeated dosing over 30 to 40 hours, fomepizole activates its own liver metabolism (via the cytochrome P450 system), which significantly speeds up how fast it is cleared from the body — shifting from a slower, saturable elimination pattern to faster first-order elimination.
📦How to store it▾
Store at 20° to 25°C (68° to 77°F).
📄 Written from Fomepizole’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Every point is grounded in that labeling — nothing is invented. How we use AI →
🩺 Pharmacist Counseling Corner
Quick, plain-English answers to the questions patients ask most about Fomepizole — the kind of thing our pharmacy team would talk through with you at the counter.
What exactly is fomepizole used for? ▾
How is fomepizole given, and will I feel it? ▾
What side effects should I watch for and when should I be worried? ▾
Can I drink alcohol while being treated with fomepizole? ▾
Are there any medications that can interfere with fomepizole? ▾
Is fomepizole safe if I have kidney or liver problems? ▾
Is Fomepizole available over the counter? ▾
When was Fomepizole first available? ▾
Who makes Fomepizole? ▾
💬 Answers drafted from Fomepizole’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Grounded in that labeling — nothing is made up. How we use AI →
🧰 Keep exploring
💊 How Fomepizole comes
Fomepizole is available in 2 forms. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Injection
How this form is used
- Fomepizole injection is used as an antidote for ethylene glycol (antifreeze) poisoning
- Fomepizole injection is used as an antidote for methanol (windshield wiper fluid) poisoning
- Fomepizole injection is used when ethylene glycol or methanol poisoning is suspected, even before it is confirmed
- Fomepizole injection may be used alone or together with hemodialysis
- Fomepizole injection is given by slow intravenous infusion over 30 minutes
- Fomepizole injection must be diluted in sterile saline or dextrose solution before administration
- Fomepizole injection dosing frequency is increased during hemodialysis — the care team will adjust the schedule
- Fomepizole injection may solidify at cool temperatures; if solid, warm the vial gently under warm water before use
Oral solution
📊 Fomepizole across the U.S. market
How Fomepizole appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
FDA-listed product records by dose form (tablet variants merged) — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
Also listed with the FDA, not a patient dose form: Powder (3) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.
Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
🔍 Compare Fomepizole products
A representative set of FDA-listed product records for Fomepizole — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Injection | ||||
| 1 g/mL | Intravenous | American Regent, Inc. × 2 listings | ANDA | View NDC → |
| 1 g/mL | Intravenous | Gland Pharma Limited | ANDA | View NDC → |
| 1 g/mL | Intravenous | Mylan Institutional LLC | ANDA | View NDC → |
| 1 g/mL | Intravenous | Navinta LLC × 3 listings | ANDA | View NDC → |
| 1.5 g/1.5 mL | Intravenous | Sagent Pharmaceuticals | ANDA | View NDC → |
| 1 g/mL | Intravenous | Zydus Pharmaceuticals USA Inc. × 3 listings | ANDA | View NDC → |
| 💊Oral solution | ||||
| 0.999 kg/0.999 kg | — | Apothecon Pharmaceuticals Pvt Ltd | BULK INGREDIENT | View NDC → |
| 2000 g/2000 g | — | Sterling Pharma Solutions Limited | BULK INGREDIENT | View NDC → |
| 💊Bulk drug substance | ||||
| 25 kg/25 kg | — | Cohance Lifesciences Limited | BULK INGREDIENT FOR HUMAN PRESCRIPTION COMPOUNDING | View NDC → |
| 1 kg/kg | — | Seratec × 2 listings | BULK INGREDIENT | View NDC → |
Showing 16 of 16 products — FDA National Drug Code Directory. See every product, package size and price: browse all 16 Fomepizole NDCs →
📈 What people report — real-world data (FDA FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Fomepizole — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Fomepizole in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
🏛️ The road to your pharmacy
How Fomepizole went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
🚨 Recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
Source: openFDA drug enforcement (recall) reports.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 15226 1 dose form · 1 strength
-
Dose form (SCDF) Injection RxCUI 1719751In current FDA listingsClinical drug / strength (SCD) 1.5 ML fomepizole 1000 MG/MLRxCUI 310414
Look up RxCUI 15226 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
📦 Supply & shortage status
Whether Fomepizole is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
🏭 Manufacturers & labelers
RxNorm drug class
Fomepizole belongs to the Antidote class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
🔬 Where this comes from
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How we combine label and product data
HelloPharmacist combines public FDA and NLM records; we don’t author the underlying clinical facts. We identified 7 FDA-filed SPL label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. The representative label is the starting point for the displayed reference monograph; the 12 largest stored in-scope SPL records, which may include that representative, are compared section by section, and the longest available version of each section is retained. Forms, routes, brands, labelers, product-listed strengths, and product-record counts are aggregated separately from ingredient-matched FDA NDC Directory records; package records listed above are associated with the linked SPL; and the normalized concept hierarchy comes from NLM RxNorm.
For canonical ingredient pages, bounded product-attributed indication and administration excerpts may be added to the AI evidence, and the generator is instructed to preserve available product, brand, route, and form qualifiers instead of treating one label as universal. Where a section is identified as AI-written, its plain-language text is generated from bounded label evidence. New draft drug pages remain in the admin review queue before first publication. Mylan Institutional LLC is the representative DailyMed label linked for verification and dates; it is not the sole source used for the page.
This is general education, not medical advice — always consult your doctor or pharmacist about your medications and any medical condition. For the exact wording of the linked representative label, view that label on DailyMed; some displayed composite sections may come from other in-scope SPL labels. Learn how we use AI and our data sources & update cadence.