FOMEPIZOLE HEMISULFATE

Details

Stereochemistry	ACHIRAL
Molecular Formula	2C4H6N2.H2O4S
Molecular Weight	262.286
Optical Activity	NONE
Defined Stereocenters	0 / 0
E/Z Centers	0
Charge	0

SHOW SMILES / InChI

Structure Search

SMILES

OS(O)(=O)=O.CC1=CNN=C1.CC2=CNN=C2

InChI

InChIKey=VOHDVKCOIZTBCU-UHFFFAOYSA-N

InChI=1S/2C4H6N2.H2O4S/c2*1-4-2-5-6-3-4;1-5(2,3)4/h2*2-3H,1H3,(H,5,6);(H2,1,2,3,4)

HIDE SMILES / InChI

Molecular Formula	C4H6N2
Molecular Weight	82.1038
Charge	0
Count

Stereochemistry	ACHIRAL
Additional Stereochemistry	No
Defined Stereocenters	0 / 0
E/Z Centers	0
Optical Activity	NONE

Molecular Formula	H2O4S
Molecular Weight	98.078
Charge	0
Count

Stereochemistry	ACHIRAL
Additional Stereochemistry	No
Defined Stereocenters	0 / 0
E/Z Centers	0
Optical Activity	NONE

Description
Sources: https://www.rxlist.com/antizol-drug.htm | https://www.tga.gov.au/sites/default/files/auspar-fomepizole-170817-pi.pdf | doi: 10.1016/B978-0-323-08500-7.00095-3

Fomepizole (4-methylpyrazole) is a competitive ADH inhibitor. Fomepizole has been shown in vitro to block alcohol dehydrogenase enzyme activity in dog, monkey and human liver. Fomepizole 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. It should be given when a known or suspected toxic ethylene glycol or methanol ingestion has occurred and the patient has metabolic acidosis and elevated osmolar gap. The most frequent adverse events reported as drug-related or unknown relationship were headache (14%), nausea (11%), and dizziness, increased drowsiness, and bad taste/metallic taste. Reciprocal interactions may occur with concomitant use of fomepizole and drugs that increase or inhibit the cytochrome P450 system (e.g. phenytoin, carbamazepine, cimetidine, ketoconazole). Fomepizole has been shown to induce the expression of CYP2E1 and to inhibit its activity. These effects were enhanced in rats that had been exposed to ethanol. Fomepizole may also inhibit other CYP enzymes and therefore may alter the exposure to other drugs that are metabolised by CYP enzymes.

Approval Year

Targets

Primary Target	Pharmacology	Condition	Potency
Alcohol dehydrogenase 6 Target ID: CHEMBL2096668 Sources: https://www.tga.gov.au/sites/default/files/auspar-fomepizole-170817-pi.pdf \| doi: 10.1016/B978-0-323-08500-7.00095-3	Inhibitor 8504

Conditions

Condition	Modality	Targets	Highest Phase	Product
Ethylene glycol Poisoning 2 Sources: https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020696	Primary		Approved 8583	ANTIZOL Approved Use 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. Launch Date 1997

C_max

Value	Dose	Analyte	Population
266.36 μM EXPERIMENT https://pubmed.ncbi.nlm.nih.gov/18344099/	15 mg/kg single, oral dose: 15 mg/kg route of administration: Oral experiment type: SINGLE co-administered:	FOMEPIZOLE serum	Homo sapiens population: HEALTHY age: ADULT sex: FEMALE / MALE food status: FASTED
355.94 μM EXPERIMENT https://pubmed.ncbi.nlm.nih.gov/18344099/	15 mg/kg single, intravenous dose: 15 mg/kg route of administration: Intravenous experiment type: SINGLE co-administered:	FOMEPIZOLE serum	Homo sapiens population: HEALTHY age: ADULT sex: FEMALE / MALE food status: FASTED
18.5 μg/mL EXPERIMENT https://www.ncbi.nlm.nih.gov/pubmed/15167624	10 mg/kg 2 times / day steady-state, oral dose: 10 mg/kg route of administration: Oral experiment type: STEADY-STATE co-administered:	FOMEPIZOLE plasma	Homo sapiens population: UNHEALTHY age: ADULT sex: FEMALE / MALE food status: UNKNOWN

AUC

Value	Dose	Co-administered	Analyte	Population
5963 μM × h EXPERIMENT https://pubmed.ncbi.nlm.nih.gov/18344099/	15 mg/kg single, oral dose: 15 mg/kg route of administration: Oral experiment type: SINGLE co-administered:		FOMEPIZOLE serum	Homo sapiens population: HEALTHY age: ADULT sex: FEMALE / MALE food status: FASTED
5922.27 μM × h EXPERIMENT https://pubmed.ncbi.nlm.nih.gov/18344099/	15 mg/kg single, intravenous dose: 15 mg/kg route of administration: Intravenous experiment type: SINGLE co-administered:		FOMEPIZOLE serum	Homo sapiens population: HEALTHY age: ADULT sex: FEMALE / MALE food status: FASTED

T_1/2

Value	Dose	Analyte	Population
21.4 h EXPERIMENT https://pubmed.ncbi.nlm.nih.gov/18344099/	15 mg/kg single, oral dose: 15 mg/kg route of administration: Oral experiment type: SINGLE co-administered:	FOMEPIZOLE serum	Homo sapiens population: HEALTHY age: ADULT sex: FEMALE / MALE food status: FASTED
17.85 h EXPERIMENT https://pubmed.ncbi.nlm.nih.gov/18344099/	15 mg/kg single, intravenous dose: 15 mg/kg route of administration: Intravenous experiment type: SINGLE co-administered:	FOMEPIZOLE serum	Homo sapiens population: HEALTHY age: ADULT sex: FEMALE / MALE food status: FASTED
14.5 h EXPERIMENT https://www.ncbi.nlm.nih.gov/pubmed/15167624	10 mg/kg 2 times / day steady-state, oral dose: 10 mg/kg route of administration: Oral experiment type: STEADY-STATE co-administered:	FOMEPIZOLE plasma	Homo sapiens population: UNHEALTHY age: ADULT sex: FEMALE / MALE food status: UNKNOWN

Doses

Dose	Population	Adverse events
100 mg/kg single, oral Highest studied dose Dose: 100 mg/kg Route: oral Route: single Dose: 100 mg/kg Sources: https://pubmed.ncbi.nlm.nih.gov/3056073	healthy, 25+/-3 Health Status: healthy Age Group: 25+/-3 Sex: M Sources: https://pubmed.ncbi.nlm.nih.gov/3056073	DLT: Nausea, Dizziness... Dose limiting toxicities: Nausea (grade 1-2, 33%) Dizziness (grade 1-2, 33%) Appetite lost (grade 1-2, 33%) Vertigo (mild, 33%) Sources: https://pubmed.ncbi.nlm.nih.gov/3056073
15 mg/kg 2 times / day multiple, intravenous Recommended Dose: 15 mg/kg, 2 times / day Route: intravenous Route: multiple Dose: 15 mg/kg, 2 times / day Sources: https://www.aafp.org/afp/1999/0701/p294.html	unhealthy Health Status: unhealthy Sex: M+F Sources: https://www.aafp.org/afp/1999/0701/p294.html	Sources: https://www.aafp.org/afp/1999/0701/p294.html

AEs

AE	Significance	Dose	Population
Appetite lost	grade 1-2, 33% DLT	100 mg/kg single, oral Highest studied dose Dose: 100 mg/kg Route: oral Route: single Dose: 100 mg/kg Sources: https://pubmed.ncbi.nlm.nih.gov/3056073	healthy, 25+/-3 Health Status: healthy Age Group: 25+/-3 Sex: M Sources: https://pubmed.ncbi.nlm.nih.gov/3056073
Dizziness	grade 1-2, 33% DLT	100 mg/kg single, oral Highest studied dose Dose: 100 mg/kg Route: oral Route: single Dose: 100 mg/kg Sources: https://pubmed.ncbi.nlm.nih.gov/3056073	healthy, 25+/-3 Health Status: healthy Age Group: 25+/-3 Sex: M Sources: https://pubmed.ncbi.nlm.nih.gov/3056073
Nausea	grade 1-2, 33% DLT	100 mg/kg single, oral Highest studied dose Dose: 100 mg/kg Route: oral Route: single Dose: 100 mg/kg Sources: https://pubmed.ncbi.nlm.nih.gov/3056073	healthy, 25+/-3 Health Status: healthy Age Group: 25+/-3 Sex: M Sources: https://pubmed.ncbi.nlm.nih.gov/3056073
Vertigo	mild, 33% DLT	100 mg/kg single, oral Highest studied dose Dose: 100 mg/kg Route: oral Route: single Dose: 100 mg/kg Sources: https://pubmed.ncbi.nlm.nih.gov/3056073	healthy, 25+/-3 Health Status: healthy Age Group: 25+/-3 Sex: M Sources: https://pubmed.ncbi.nlm.nih.gov/3056073

Sourcing

Vendor/Aggregator	ID	URL
ChEBI	CHEBI:5141	https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:5141
ChemicalBook	CB8233079	https://www.chemicalbook.com/ChemicalProductProperty_EN_CB8233079
eMolecules	489528	https://www.emolecules.com/cgi-bin/more?vid=489528
MolPort	MolPort-016-633-159	https://www.molport.com/shop/molecule-link/MolPort-016-633-159
ZINC	ZINC000000897288	http://zinc15.docking.org/substances/ZINC000000897288

PubMed

Title	Date	PubMed
Metabolism of 3-methylindole by porcine liver microsomes: responsible cytochrome P450 enzymes.	2000 Jun	10828259
Treatment of acute methanol poisoning with fomepizole.	2001 Aug	11511951
Bioactivation to free radicals and cytotoxicity of 1,1-dichloro-1-fluoroethane (HCFC-141b).	2001 Feb	11407538
Metabolism of styrene in the human liver in vitro: interindividual variation and enantioselectivity.	2001 Feb	11407535
Oxidation of 2,6-dimethylaniline by recombinant human cytochrome P450s and human liver microsomes.	2001 Jun	11409937
Tissue-specific alterations in the 6-hydroxylation of chlorzoxazone following traumatic brain injury in the rat.	2001 Mar	11181498
Ethanol inhibits the JAK-STAT signaling pathway in freshly isolated rat hepatocytes but not in cultured hepatocytes or HepG2 cells: evidence for a lack of involvement of ethanol metabolism.	2001 May	11408018
Functional relevance of human adh polymorphism.	2001 May	11391066
The role of the liver in the acute effect of alcohol on androgens in women.	2001 May	11344195
Inhibition of alcohol dehydrogenase blocks enhanced Gi-protein expression following ethanol treatment in experimental hepatocellular carcinoma in vitro.	2001 Oct	11711778
Mechanism of aerobic transformation of carbon tetrachloride by poplar cells.	2002	12688582
American Academy of Clinical Toxicology practice guidelines on the treatment of methanol poisoning.	2002	12216995
Rat ventral prostate microsomal biotransformation of ethanol to acetaldehyde and 1-hydroxyethyl radicals: its potential contribution to prostate tumor promotion.	2002	12210496
Comparison of the therapeutic efficacy of 4-methylpyrazole and N-acetylcysteine on acetaminophen (paracetamol) hepatotoxicity in rats.	2002	12017214
Treatment of a 1,4-butanediol poisoning with fomepizole.	2002	11990207
Overexpression of alcohol dehydrogenase exacerbates ethanol-induced contractile defect in cardiac myocytes.	2002 Apr	11893554
Central effects of 1,4-butanediol are mediated by GABA(B) receptors via its conversion into gamma-hydroxybutyric acid.	2002 Apr 26	12063087
Role of endotoxin in NF-kappaB activation by ethanol in rat hepatocytes.	2002 Aug	12198367
Oxidative bioactivation of crotyl alcohol to the toxic endogenous aldehyde crotonaldehyde: association of protein carbonylation with toxicity in mouse hepatocytes.	2002 Aug	12184789
PAV-1, a new rat hepatic stellate cell line converts retinol into retinoic acid, a process altered by ethanol.	2002 Aug	12007639
Fomepizole therapy for reversal of visual impairment after methanol poisoning: a case documented by visual evoked potentials investigation.	2002 Dec	12470767
Spectroscopic study on charge transfer molecular complexes of pyrazole derivatives with some pi-electron acceptors.	2002 Jul	12164488
Fomepizole as an antidote for ethylene glycol poisoning.	2002 Jun	12022913
Accreditation of skin from a methanol-poisoned victim for banking and grafting.	2002 Jun 27	12131687
Reduction of toxic metabolite formation of acetaminophen.	2002 Mar 8	11866476
Suppression of the contact hypersensitivity response following topical exposure to 2-butoxyethanol in female BALB/c mice.	2002 Mar-Apr	12022630
Comparative metabolism of N-tert-butyl-N-[1-(1-oxy-pyridin-4-yl)-ethyl]- and N-tert-butyl-N-(1-phenyl-ethyl)-nitroxide by the cytochrome P450 monooxygenase system.	2002 May	12018998
The effect of cyanamide and 4-methylpyrazole on the ethanol-induced locomotor activity in mice.	2002 May	11900810
Mediation by nitric oxide of the stimulatory effects of ethanol on blood flow.	2002 May 10	12138012
[Severe ethylene glycol poisoning treated wtih fomepizole (4-methylpyrazole)].	2002 Oct 20	12448112
Rethinking the toxic methanol level.	2003	14677789
Ethylene glycol intoxication: case report and pharmacokinetic perspectives.	2003 Dec	14695045
Are there teratogenic risks associated with antidotes used in the acute management of poisoned pregnant women?	2003 Feb	12769509
Cinnamic compound metabolism in human skin and the role metabolism may play in determining relative sensitisation potency.	2003 Feb	12615359
Inhalational methanol toxicity in pregnancy treated twice with fomepizole.	2003 Feb	12583693
Agitation by sedation.	2003 Jan 25	12559866
Antidote review: fomepizole for methanol poisoning.	2003 Jan-Feb	12522524
Metabolism of chloroform in the human liver and identification of the competent P450s.	2003 Mar	12584152
Species variations in cutaneous alcohol dehydrogenases and aldehyde dehydrogenases may impact on toxicological assessments of alcohols and aldehydes.	2003 Mar 3	12499113
Allyl alcohol activation of protein kinase C delta leads to cytotoxicity of rat hepatocytes.	2003 May	12755590
Methanol ingestion: prevention of toxic sequelae after massive ingestion.	2003 May	12745047
In vivo formation of salsolinol induced by high acetaldehyde concentration in rat striatum employing microdialysis.	2003 May-Jun	12711651
Increased prooxidant production and enhanced susceptibility to glutathione depletion in HepG2 cells co-expressing HCV core protein and CYP2E1.	2004 Feb	14695664

Patents

Sample Use Guides

In Vivo Use Guide

A loading dose of 15 mg/kg should be administered, followed by doses of 10 mg/kg every 12 hours for 4 doses, then 15 mg/kg every 12 hours thereafter until ethylene glycol or methanol concentrations are undetectable or have been reduced below 20 mg/dL (ethylene glycol 3.22 mmol/L, methanol 6.24 mmol/L), and the patient is asymptomatic with normal pH. All doses should be administered as a slow intravenous infusion over 30 minutes

Route of Administration: Intravenous

Substance Class	Chemical Created by `admin` on `Mon Mar 31 21:35:03 GMT 2025` Edited by `admin` on `Mon Mar 31 21:35:03 GMT 2025`
Record UNII	93AY3O3G2W
Record Status	`Validated (UNII)`
Record Version

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Name

Type

Language

FOMEPIZOLE SULFATE

Preferred Name

English

FOMEPIZOLE HEMISULFATE

Common Name

English

Fomepizole hemisulfate [WHO-DD]

Common Name

English

FOMEPIZOLE SULPHATE

Common Name

English

1H-PYRAZOLE, 4-METHYL-, SULFATE

Systematic Name

English

Code System Code Type Description

EVMPD

SUB78296