OpenClaim

Fomepizole Side Effects

The most commonly reported side effects of fomepizole include toxicity to various agents, overdose, and off label use, based on 193 FDA adverse event reports from 2004 to 2025. 33.7% of reports found the drug to be ineffective.

#1 Reported: Toxicity To Various AgentsAll side effects ↓Top Co-Medication: AcetaminophenDrug interactions ↓84% of Reports Are AdultDemographics ↓

Fomepizole side effects

Percentages show how often each reaction appears relative to total reports for fomepizole.

1
Drug Ineffective33.7%65
2
Toxicity To Various Agents25.4%49
3
Overdose19.2%37
4
Off Label Use15.0%29
5
Metabolic Acidosis11.4%22
6
Hepatotoxicity8.8%17
7
Intentional Overdose8.8%17
8
Hypotension8.3%16
9
Acute Kidney Injury8.3%16
10
Drug-induced Liver Injury6.7%13
11
Brain Oedema6.2%12
12
Encephalopathy6.2%12
13
Drug Ineffective For Unapproved Indication6.2%12
14
Hypoglycaemia5.7%11
15
Acute Hepatic Failure5.2%10

These are voluntary reports and do not establish that fomepizole caused these reactions.

Report severity

96.9%Serious187 reports
69.4%Hospitalizations134 reports
33.2%Fatal64 reports

Seriousness is determined by the reporter, not by OpenClaim.

Fomepizole drug interactions

Other drugs that appear in adverse event reports alongside fomepizole. Drugs flagged as a suspected cause appear in the first column. Drugs taken at the same time but not suspected appear in the second.

Also suspected

1
Acetaminophen32.1%62
2
Acetylcysteine21.8%42
3
Sodium-bicarbonate19.2%37
4
Thiamine16.1%31
5
Epinephrine13.0%25
6
Pyridoxine12.4%24
7
Vasopressin9.3%18
8
Folic-acid9.3%18
9
Phenylephrine6.2%12
10
Metformin5.7%11
11
Dextrose5.2%10
12
Vitamin-k3.6%7
13
Ibuprofen3.1%6
14
Calcium3.1%6
15
Levoleucovorin3.1%6

Taken alongside

1
Acetaminophen5.7%11
2
Acetylcysteine4.7%9
3
Sodium-bicarbonate3.6%7
4
Thiamine3.1%6
5
Lorazepam3.1%6
6
Folic-acid3.1%6
7
Insulin2.6%5
8
Pyridoxine2.6%5
9
Apomorphine-hydrochloride2.1%4
10
Albuterol2.1%4
11
Ergocalciferol2.1%4
12
Metoprolol2.1%4
13
Oxycodone2.1%4
14
Alcohol2.1%4
15
Esomeprazole1.6%3

Co-occurrence in adverse event reports does not establish a drug interaction. Patients often take multiple medications, and these lists reflect prescribing patterns rather than causal relationships. Consult a healthcare provider about potential drug interactions.

Who reports fomepizole side effects

40.4% of fomepizole adverse event reports involve female patients and 44.6% involve male patients. The largest age group is adult at 84%. These figures reflect who reports side effects, not underlying risk.

Sex

Female40.4%
Male44.6%
Unknown15.0%

Age group

< 20.0%
2–111.2%
12–179.2%
18–6484.0%
65+5.5%

What is fomepizole used for

Conditions and purposes for which patients were taking fomepizole when the adverse event was reported.

Accidental OverdoseAccidental PoisoningAlcohol PoisoningAlcohol UseAnaphylactic ReactionAccidental OverdoseAcute Hepatic FailureAdjuvant TherapyAlcohol PoisoningAnalgesic Drug Level IncreasedAspirationBlood Methanol IncreasedChemical PoisoningDiabetes MellitusDrug Therapy

Showing 15 of 41 indications

Fomepizole brand names and reporting trend

Fomepizole is sold under the brand name Antizol.

Brand names

Antizol213

Quarterly reports (2004–2025)

200420202025

An upward trend reflects increased FAERS reporting overall, not necessarily increased risk.

Taking fomepizole with another medication?

Ask OpenClaim about your specific drug combination. Get a sourced report using FDA data, drug labels, and medical literature.

Check my medications