Disulfiram

Disulfiram is used as a second-line treatment, behind acamprosate and naltrexone, for alcohol dependence.[3]

Under normal metabolism, alcohol is broken down in the liver by the enzyme alcohol dehydrogenase to acetaldehyde, which is then converted by the enzyme acetaldehyde dehydrogenase to a harmless acetic acid derivative (acetyl coenzyme A). Disulfiram blocks this reaction at the intermediate stage by blocking acetaldehyde dehydrogenase. After alcohol intake under the influence of disulfiram, the concentration of acetaldehyde in the blood may be five to 10 times higher than that found during metabolism of the same amount of alcohol alone. As acetaldehyde is one of the major causes of the symptoms of a "hangover", this produces immediate and severe negative reaction to alcohol intake. About 5 to 10 minutes after alcohol intake, the patient may experience the effects of a severe hangover for a period of 30 minutes up to several hours. Symptoms usually include flushing of the skin, accelerated heart rate, low blood pressure, nausea, and vomiting. Uncommon adverse events include shortness of breath, throbbing headache, visual disturbance, mental confusion, postural syncope, and circulatory collapse.[4]

Disulfiram should not be taken if alcohol has been consumed in the last 12 hours.[5] There is no tolerance to disulfiram: the longer it is taken, the stronger its effects.[2] As disulfiram is absorbed slowly through the digestive tract and eliminated slowly by the body, the effects may last for up to two weeks after the initial intake; consequently, medical ethics dictate that patients must be fully informed about the disulfiram-alcohol reaction.[6]

Disulfiram does not reduce alcohol cravings, so a major problem associated with this drug is extremely poor compliance. Methods to improve compliance include subdermal implants, which release the drug continuously over a period of up to 12 weeks, and supervised administration practices, for example, having the drug regularly administered by one's spouse.

Although disulfiram remained the most common pharmaceutical treatment of alcohol abuse until the end of the 20th century, today it is often replaced or accompanied with newer drugs, primarily the combination of naltrexone and acamprosate, which directly attempt to address physiological processes in the brain associated with alcohol abuse.

The most common side effects in the absence of alcohol are headache, and a metallic or garlic taste in the mouth, though more severe side effects may occur.[7] Tryptophol, a chemical compound that induces sleep in humans, is formed in the liver after disulfiram treatment.[8] Less common side effects include decrease in libido, liver problems, skin rash, and nerve inflammation.[9] Liver toxicity is an uncommon but potentially serious side effect, and risk groups e.g. those with already impaired liver function should be monitored closely. That said, the rate of disulfiram-induced hepatitis are estimated to be in between 1 per 25,000 to 1 in 30,000,[10] and rarely the primary cause for treatment cessation.

Cases of disulfiram neurotoxicity have also occurred, causing extrapyramidal and other symptoms.[11] Disulfiram can produce neuropathy in daily doses of less than the usually recommended 500 mg. Nerve biopsies showed axonal degeneration and the neuropathy is difficult to distinguish from that associated with ethanol abuse. Disulfiram neuropathy occurs after a variable latent period (mean 5 to 6 months) and progresses steadily. Slow improvement may occur when the drug's use is stopped; often there is complete recovery eventually.[12]

Disulfiram disrupts metabolism of several other compounds, including paracetamol (acetaminophen),[13] theophylline[14] and caffeine.[15] However, in most cases, this disruption is mild and presents itself as a 20–40% increase in the half-life of the compound at typical dosages of disulfiram.

In medicine, the term "disulfiram effect" refers to an adverse effect of a particular medication in causing an unpleasant hypersensitivity to alcohol, similar to the effect caused by disulfiram administration.

Examples:

• Antibiotics (nitroimidazoles), e.g. metronidazole
• First-generation sulfonylureas, e.g. tolbutamide and chlorpropamide
• Several cephalosporin drugs, including cefoperazone, cefamandole and cefotetan, that have a N-methylthio-tetrazole moiety
• Griseofulvin, an oral antifungal drug
• Procarbazine
• Temposil, or citrated calcium carbimide, has the same function as disulfiram, but is weaker and safer.
• Coprine, which metabolizes to 1-aminocyclopropanol, a chemical having the same metabolic effects as disulfiram. It occurs naturally in the otherwise edible common ink cap mushroom (Coprinopsis atramentaria), hence its colloquial name "tippler's bane". Similar reactions have been recorded with Clitocybe clavipes and Suillellus luridus, although the agent in those species is unknown.

The synthesis of disulfiram, originally known as tetraethylthiuram disulfide, was first reported in 1881. By around 1900, it was introduced to the industrial process of sulfur vulcanization of rubber and became widely used. In 1937 a plant physician in the American rubber industry described adverse reactions to alcohol in workers exposed to tetramethylthiuram monosulfide and disulfide, and proposed that this effect of disulfiram and related compounds might lead to ”the cure for alcoholism”; the effect was also noticed in workers at a Swedish rubber boot factory.[16]

In the early 1940s it had been tested as a treatment for scabies, a parasitic skin infection, as well as intestinal worms.[16]

Around that time, during the German occupation of Denmark, Erik Jacobsen and Jens Hald at the Danish drug company Medicinalco picked up on that research and began exploring the use of disulfiram to treat intestinal parasites. The company had a group of enthusiastic self-experimenters that called itself the "Death Battalion", and in the course of testing the drug on themselves, accidentally discovered that drinking alcohol while the drug was still in their bodies made them mildly sick.[16][17]^: 98–105

They made that discovery in 1945, and did nothing with it until two years later, when Jacobsen gave an impromptu talk and mentioned that work, which was discussed afterwards in newspapers at the time, leading them to further explore the use of the drug for that purpose.[16][17]^: 98–105 That work included small clinical trials with Oluf Martensen-Larsen, a doctor who worked with alcoholics.[16] They published their work starting in 1948.[16][18]

The chemists at Medicinalco discovered a new form of disulfiram while trying to purify a batch that had been contaminated with copper. This form turned out to have better pharmacological properties, and the company patented it and used that form for the product that was introduced as Antabus (later anglicized to Antabuse).[16]

This work led to renewed study of the human metabolism of ethanol. It was already known that ethanol was mostly metabolized in the liver, with it being converted first to acetaldehyde and then acetaldehyde to acetic acid and carbon dioxide, but the enzymes involved were not known. By 1950 the work led to the knowledge that ethanol is oxidized to acetaldehyde by alcohol dehydrogenase and acetaldehyde is oxidized to acetic acid by aldehyde dehydrogenase (ALDH), and that disulfiram works by inhibiting ALDH, leading to a buildup of acetaldehyde, which is what causes the negative effects in the body.[16]

The drug was first marketed in Denmark and as of 2008, Denmark is the country where it is most widely prescribed. It was approved by the FDA in 1951.[16][19] The FDA later approved other drugs for treatment of alcoholism, namely naltrexone in 1994 and acamprosate in 2004.[16]

Though the Occupational Safety and Health Administration (OSHA) in the US has not set a permissible exposure limit (PEL) for disulfiram in the workplace, the National Institute for Occupational Safety and Health has set a recommended exposure limit (REL) of 2 mg/m³ and recommended that workers avoid concurrent exposure to ethylene dibromide.[20]

Disulfiram has been studied as a possible treatment for cancer,[21] parasitic infections,[22] anxiety disorder,[23] and latent HIV infection.[24]

Disulfiram has shown reversing of retinitis pigmentosa in rats.[25][26][27]

• "Disulfiram". Drug Information Portal. U.S. National Library of Medicine.
• Toxicity, Mushroom - Disulfiramlike Toxins at eMedicine
• CDC - NIOSH Pocket Guide to Chemical Hazards