Fomepizole

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Fomepizole
Fomepizole.svg
Fomepizole 3D ball.png
Chemical structure of fomepizole
Clinical data
Pronunciation /ˌfˈmɛpɪzl/
Trade names Antizol, others
Other names4-Methylpyrazole
AHFS/Drugs.com Monograph
License data
Routes of
administration
Intravenous
ATC code
Legal status
Legal status
Identifiers
  • 4-Methyl-1H-pyrazole
CAS Number
PubChem CID
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard 100.028.587 OOjs UI icon edit-ltr-progressive.svg
Chemical and physical data
Formula C4H6N2
Molar mass 82.106 g·mol−1
3D model (JSmol)
Density 0.99 g/cm3
Boiling point 204 to 207 °C (399 to 405 °F) (at 97,3 kPa)
  • CC1=CNN=C1
  • InChI=1S/C4H6N2/c1-4-2-5-6-3-4/h2-3H,1H3,(H,5,6) Yes check.svgY
  • Key:RIKMMFOAQPJVMX-UHFFFAOYSA-N

Fomepizole, also known as 4-methylpyrazole, is a medication used to treat methanol and ethylene glycol poisoning. [4] It may be used alone or together with hemodialysis. [4] It is given by injection into a vein. [4]

Contents

Common side effects include headache, nausea, sleepiness, and unsteadiness. [4] It is unclear if use during pregnancy causes risk to a fetus. [4] Fomepizole works by blocking the enzyme that converts methanol and ethylene glycol to their toxic breakdown products. [4]

Fomepizole was approved for medical use in the United States in 1997. [4] It is on the World Health Organization's List of Essential Medicines. [5]

Medical use

Fomepizole is used to treat ethylene glycol and methanol poisoning. It acts to inhibit the breakdown of these toxins into their active toxic metabolites. Fomepizole is a competitive inhibitor of the enzyme alcohol dehydrogenase, [6] found in the liver. This enzyme plays a key role in the metabolism of ethylene glycol, and of methanol.

By competitively inhibiting the first enzyme, alcohol dehydrogenase, in the metabolism of ethylene glycol and methanol, fomepizole slows the production of the toxic metabolites. The slower rate of metabolite production allows the liver to process and excrete the metabolites as they are produced, limiting the accumulation in tissues such as the kidney and eye. As a result, much of the organ damage is avoided. [8]

Fomepizole is most effective when given soon after ingestion of ethylene glycol or methanol. Delaying its administration allows for the generation of harmful metabolites. [8]

Interaction with alcohol

Concurrent use with ethanol is contraindicated because fomepizole is known to prolong the half-life of ethanol via inhibiting its metabolism. Extending the half-life of ethanol may increase and extend the intoxicating effects of ethanol, allowing for greater (potentially dangerous) levels of intoxication at lower doses. Fomepizole slows the production of acetaldehyde by inhibiting alcohol dehydrogenase, which in turn allows more time to further convert acetaldehyde into acetic acid by acetaldehyde dehydrogenase. The result is a patient with a prolonged and deeper level of intoxication for any given dose of ethanol, and reduced "hangover" symptoms (since these adverse symptoms are largely mediated by acetaldehyde build up).

In a chronic alcoholic who has built up a tolerance to ethanol, this removes some of the disincentives to ethanol consumption ("negative reinforcement") while allowing them to become intoxicated with a lower dose of ethanol. The danger is that the alcoholic will then overdose on ethanol (possibly fatally). If alcoholics instead very carefully reduce their doses to reflect the now slower metabolism, they may get the "rewarding" stimulus of intoxication at lower doses with less adverse "hangover" effects - leading potentially to increased psychological dependency. However, these lower doses may therefore produce less chronic toxicity and provide a harm minimization approach to chronic alcoholism.

It is, in essence, the antithesis of a disulfiram approach which tries to increase the buildup of acetaldehyde resulting in positive punishment for the patient. Compliance, and adherence, is a substantial problem in disulfiram-based approaches. Disulfiram also has a considerably longer half-life than that of fomepizole, requiring the person to not drink ethanol in order to avoid severe effects. If the person is not adequately managed on a benzodiazepine, barbiturate, acamprosate, or another GABAA receptor agonist, the alcohol withdrawal syndrome, and its attendant, life-threatening risk of delirium tremens "DT", may occur. Disulfiram treatment should never be initiated until the risk of DT has been evaluated, and mitigated appropriately. Fomepizole treatment may be initiated while the DT de-titration sequence is still being calibrated based upon the person's withdrawal symptoms and psychological health.[ citation needed ]

Adverse effects

Common side effects associated with fomepizole use include headache and nausea. [9]

Kinetics

Absorption and distribution

Fomepizole distributes rapidly into total body water. The volume of distribution is between 0.6 and 1.02 L/kg. The therapeutic concentration is from 8.2 to 24.6 mg (100 to 300 micromoles) per liter. Peak concentration following single oral doses of 7 to 50 mg/kg of body weight occurred in 1 to 2 hours. The half-life varies with dose, so has not been calculated.

Metabolism and elimination

Hepatic; the primary metabolite is 4-carboxypyrazole (about 80 to 85% of an administered dose). Other metabolites include the pyrazoles 4-hydroxymethylpyrazole and the N -glucuronide conjugates of 4-carboxypyrazole and 4-hydroxymethylpyrazole.

Following multiple doses, fomepizole rapidly induces its own metabolism via the cytochrome P450 mixed-function oxidase system.

In healthy volunteers, 1.0 to 3.5% of an administered dose was excreted unchanged in the urine. The metabolites also are excreted unchanged in the urine.

Fomepizole is dialyzable.

Other uses

Apart from medical uses, the role of 4-methylpyrazole in coordination chemistry has been studied. [10]

Related Research Articles

<span class="mw-page-title-main">Ethanol</span> Organic compound (CH₃CH₂OH)

Ethanol is an organic compound with the chemical formula CH3CH2OH. It is an alcohol, with its formula also written as C2H5OH, C2H6O or EtOH, where Et stands for ethyl. Ethanol is a volatile, flammable, colorless liquid with a characteristic wine-like odor and pungent taste. It is a psychoactive recreational drug, and the active ingredient in alcoholic drinks.

Acetaldehyde (IUPAC systematic name ethanal) is an organic chemical compound with the formula CH3 CHO, sometimes abbreviated as MeCHO. It is a colorless liquid or gas, boiling near room temperature. It is one of the most important aldehydes, occurring widely in nature and being produced on a large scale in industry. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced by plants. It is also produced by the partial oxidation of ethanol by the liver enzyme alcohol dehydrogenase and is a contributing cause of hangover after alcohol consumption. Pathways of exposure include air, water, land, or groundwater, as well as drink and smoke. Consumption of disulfiram inhibits acetaldehyde dehydrogenase, the enzyme responsible for the metabolism of acetaldehyde, thereby causing it to build up in the body.

<span class="mw-page-title-main">Alcohol dehydrogenase</span> Group of dehydrogenase enzymes

Alcohol dehydrogenases (ADH) (EC 1.1.1.1) are a group of dehydrogenase enzymes that occur in many organisms and facilitate the interconversion between alcohols and aldehydes or ketones with the reduction of nicotinamide adenine dinucleotide (NAD+) to NADH. In humans and many other animals, they serve to break down alcohols that are otherwise toxic, and they also participate in the generation of useful aldehyde, ketone, or alcohol groups during the biosynthesis of various metabolites. In yeast, plants, and many bacteria, some alcohol dehydrogenases catalyze the opposite reaction as part of fermentation to ensure a constant supply of NAD+.

<span class="mw-page-title-main">Disulfiram</span> Chemical compound

Disulfiram is a medication used to support the treatment of chronic alcoholism by producing an acute sensitivity to ethanol. Disulfiram works by inhibiting the enzyme aldehyde dehydrogenase, causing many of the effects of a hangover to be felt immediately following alcohol consumption. Disulfiram plus alcohol, even small amounts, produces flushing, throbbing in the head and neck, a throbbing headache, respiratory difficulty, nausea, copious vomiting, sweating, thirst, chest pain, palpitation, dyspnea, hyperventilation, fast heart rate, low blood pressure, fainting, marked uneasiness, weakness, vertigo, blurred vision, and confusion. In severe reactions there may be respiratory depression, cardiovascular collapse, abnormal heart rhythms, heart attack, acute congestive heart failure, unconsciousness, convulsions, and death.

<span class="mw-page-title-main">Acetaldehyde dehydrogenase</span> Class of enzymes

Acetaldehyde dehydrogenases are dehydrogenase enzymes which catalyze the conversion of acetaldehyde into acetyl-CoA. This can be summarized as follows:

Toxication, toxification or toxicity exaltation is the conversion of a chemical compound into a more toxic form in living organisms or in substrates such as soil or water. The conversion can be caused by enzymatic metabolism in the organisms, as well as by abiotic chemical reactions. While the parent drug are usually less active, both the parent drug and its metabolite can be chemically active and cause toxicity, leading to mutagenesis, teratogenesis, and carcinogenesis. Different classes of enzymes, such as P450-monooxygenases, epoxide hydrolase, or acetyltransferases can catalyze the process in the cell, mostly in the liver.

<span class="mw-page-title-main">Alcohol flush reaction</span> Effect of alcohol consumption on the human body

Alcohol flush reaction is a condition in which a person develops flushes or blotches associated with erythema on the face, neck, shoulders, ears, and in some cases, the entire body after consuming alcoholic beverages. The reaction is the result of an accumulation of acetaldehyde, a metabolic byproduct of the catabolic metabolism of alcohol, and is caused by an aldehyde dehydrogenase 2 deficiency.

<span class="mw-page-title-main">Diethylene glycol</span> Chemical compound

Diethylene glycol (DEG) is an organic compound with the formula (HOCH2CH2)2O. It is a colorless, practically odorless, and hygroscopic liquid with a sweetish taste. It is a four carbon dimer of ethylene glycol. It is miscible in water, alcohol, ether, acetone, and ethylene glycol. DEG is a widely used solvent. It can be a normal ingredient in various consumer products, and it can be a contaminant. DEG has also been misused to sweeten wine and beer, and to viscosify oral and topical pharmaceutical products. Its use has resulted in many epidemics of poisoning since the early 20th century.

<span class="mw-page-title-main">Hangover</span> Discomfort following alcohol consumption

A hangover is the experience of various unpleasant physiological and psychological effects usually following the consumption of alcohol, such as wine, beer, and liquor. Hangovers can last for several hours or for more than 24 hours. Typical symptoms of a hangover may include headache, drowsiness, concentration problems, dry mouth, dizziness, fatigue, gastrointestinal distress, absence of hunger, light sensitivity, depression, sweating, hyper-excitability, irritability, and anxiety.

<span class="mw-page-title-main">1,1,2,2-Tetrachloroethane</span> Chemical compound

1,1,2,2-tetrachloroethane (TeCA), also known by the brand names Bonoform, Cellon and Westron, is an organic compound. It is colorless liquid and has a sweet odor. It is used as an industrial solvent and as a separation agent. TeCA is toxic and it can be inhaled, consumed or absorbed through the skin. After exposure, nausea, dizziness or even liver damage may occur.

Ethylene glycol poisoning is poisoning caused by drinking ethylene glycol. Early symptoms include intoxication, vomiting and abdominal pain. Later symptoms may include a decreased level of consciousness, headache, and seizures. Long term outcomes may include kidney failure and brain damage. Toxicity and death may occur after drinking even in a small amount as ethylene glycol is more toxic than other diols.

<span class="mw-page-title-main">High anion gap metabolic acidosis</span> Medical condition

High anion gap metabolic acidosis is a form of metabolic acidosis characterized by a high anion gap. Metabolic acidosis occurs when the body produces too much acid, or when the kidneys are not removing enough acid from the body. Several types of metabolic acidosis occur, grouped by their influence on the anion gap.

Isopropyl alcohol is a colorless, flammable organic compound with a pungent alcoholic odor.

<span class="mw-page-title-main">Coprine</span> Chemical compound

Coprine is a mycotoxin. It was first isolated from common inkcap. It occurs in mushrooms in the genera Coprinopsis. When combined with alcohol, it causes "Coprinus syndrome". It inhibits the enzyme acetaldehyde dehydrogenase, which is involved in the metabolism of alcohol. This inhibition leads to a buildup of acetaldehyde, causing an alcohol flush reaction. Because of this, the mushroom is commonly referred to as Tippler's Bane.

<span class="mw-page-title-main">Jeffrey Brent</span> Medical toxicologist

Jeffrey A. Brent is a medical toxicologist who is a distinguished clinical professor of medicine and emergency medicine at the University of Colorado, School of Medicine. In addition, he is a professor at the Department of Environmental and Occupational Health at the Colorado School of Public Health. He is also the past president of the American Academy of Clinical Toxicology, was editor in chief of the journal Toxicological Reviews, and was a member of the board of directors of the American College of Medical Toxicology. Previously, most of Brent's research focused on the use of fomepizole as a treatment for both methanol and ethylene glycol poisoning, and he led a trial of this drug which resulted in the FDA approving it in December 1997. Currently, Brent serves as Director of the Toxicology Investigators Consortium, an NIH and FDA supported multi center research and surveillance group. Brent is also a senior editor of "Critical Care Toxicology: Diagnosis and Management of the Critically Poisoned Patient," originally published in 2005, and now in its second edition, which was published in 2017.

<span class="mw-page-title-main">Methanol toxicity</span> Medical condition

Methanol toxicity is poisoning from methanol, characteristically via ingestion. Symptoms may include a decreased level of consciousness, poor or no coordination, vomiting, abdominal pain, and a specific smell on the breath. Decreased vision may start as early as twelve hours after exposure. Long-term outcomes may include blindness and kidney failure. Blindness may occur after drinking as little as 10 mL; death may occur after drinking quantities over 15 mL.

<span class="mw-page-title-main">Alcohol (drug)</span> Active ingredient in alcoholic beverages

Alcohol, sometimes referred to by the chemical name ethanol, is a depressant drug that is the active ingredient in fermented drinks such as beer, wine, and distilled spirits. It is one of the oldest and most commonly consumed recreational drugs, causing the characteristic effects of alcohol intoxication ("drunkenness"). Among other effects, alcohol produces happiness and euphoria, decreased anxiety, increased sociability, sedation, impairment of cognitive, memory, motor, and sensory function, and generalized depression of central nervous system (CNS) function.

<span class="mw-page-title-main">Alcohol intolerance</span> Medical condition

Alcohol intolerance is due to a genetic polymorphism of the aldehyde dehydrogenase enzyme, which is responsible for the metabolism of acetaldehyde. This polymorphism is most often reported in patients of East Asian descent. Alcohol intolerance may also be an associated side effect of certain drugs such as disulfiram, metronidazole, or nilutamide. Skin flushing and nasal congestion are the most common symptoms of intolerance after alcohol ingestion. It may also be characterized as intolerance causing hangover symptoms similar to the "disulfiram-like reaction" of aldehyde dehydrogenase deficiency or chronic fatigue syndrome. Severe pain after drinking alcohol may indicate a more serious underlying condition.

<span class="mw-page-title-main">Alcohols (medicine)</span> Alcohols used as antiseptics, disinfectants or antidotes

Alcohols, in various forms, are used within medicine as an antiseptic, disinfectant, and antidote. Alcohols applied to the skin are used to disinfect skin before a needle stick and before surgery. They may be used both to disinfect the skin of the person and as hand sanitizer of the healthcare providers. They can also be used to clean other areas and in mouthwashes. Taken by mouth or injected into a vein, ethanol is used to treat methanol or ethylene glycol toxicity when fomepizole is not available.

<span class="mw-page-title-main">Disulfiram-like drug</span> Drug that causes an adverse reaction to alcohol

A disulfiram-like drug is a drug that causes an adverse reaction to alcohol leading to nausea, vomiting, flushing, dizziness, throbbing headache, chest and abdominal discomfort, and general hangover-like symptoms among others. These effects are caused by accumulation of acetaldehyde, a major but toxic metabolite of alcohol formed by the enzyme alcohol dehydrogenase. The reaction has been variously termed a disulfiram-like reaction, alcohol intolerance, and acetaldehyde syndrome.

References

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