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Ethyl carbamate
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Ethyl carbamate
Ethyl carbamate (also called urethane) is an organic compound with the formula CH3CH2OC(O)NH2. It is an ester of carbamic acid and a white solid. Despite its name, it is not a component of polyurethanes. Because it is a carcinogen, it is rarely used, but naturally forms in low quantities in many types of fermented foods and drinks.
It is produced industrially by heating urea and ethyl alcohol. It also arises by the action of ammonia on ethyl chloroformate.
Ethyl carbamate has been used as an antineoplastic agent and for other medicinal purposes, but this application ended after it was discovered to be carcinogenic in 1943. However, Japanese usage in medical injections continued and from 1950 to 1975 an estimated 100 million 2 ml ampules of 7-to-15% solutions of ethyl carbamate were injected into patients as a co-solvent in water for dissolving water-insoluble analgesics used for post-operation pain. These doses were estimated to be at levels that are carcinogenic in mice. This practice was stopped in 1975. "This regrettable medical situation appears to have involved the largest number (millions) of humans exposed to the largest doses of a pure carcinogen that is on record". The author, U.S. cancer researcher James A. Miller, called for studies to determine the effects on Japanese cancer rates to be performed but apparently none were ever done.[citation needed]
Prior to World War II, ethyl carbamate saw relatively heavy use in the treatment of multiple myeloma before it was found to be toxic, carcinogenic, and largely ineffective. By US FDA regulations, ethyl carbamate has been withdrawn from pharmaceutical use. However, small quantities of ethyl carbamate are also used in laboratories as an anesthetic for animals.
Ethyl carbamate was reclassified as a Group 2A carcinogen by IARC in 2007.
Ethyl carbamate is used as an anaesthetic in animal experiments, with more than 100 animal studies using ethyl carbamate published each year. One advantage of using ethyl carbamate is that it has a very long duration of action, with some adult rats remaining anaesthetised 24 hours after administration of the drug. It also does not depress neuronal activity in the cortex to the same extent as isoflurane.
Formerly, ethyl carbamate was used as a chemical intermediate in the preparation of amino resins, that were in turn used as crosslinking agents for permanent-press textile treatments to create "wash-and-wear" fabrics. Other uses included as solvent or intermediary in the manufacture of pesticides, cosmetics and pharmaceuticals.
The widespread presence of ethyl carbamate in alcoholic beverages was discovered during the mid-1980s. To raise public awareness of this issue, the U.S. Center for Science in the Public Interest published, in 1987, Tainted Booze: The Consumer's Guide to Urethane in Alcoholic Beverages. Studies have shown that most, if not all, yeast-fermented alcoholic beverages contain traces of ethyl carbamate (15 ppb to 12 ppm). Other foods and beverages prepared by means of fermentation also contain ethyl carbamate. For example, bread has been found to contain 2 ppb; as much as 20 ppb has been found in some samples of soy sauce. Amounts of both ethyl carbamate and methyl carbamate have also been found in wines, sake, beer, brandy, whiskey and other fermented alcoholic beverages.
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Ethyl carbamate
Ethyl carbamate (also called urethane) is an organic compound with the formula CH3CH2OC(O)NH2. It is an ester of carbamic acid and a white solid. Despite its name, it is not a component of polyurethanes. Because it is a carcinogen, it is rarely used, but naturally forms in low quantities in many types of fermented foods and drinks.
It is produced industrially by heating urea and ethyl alcohol. It also arises by the action of ammonia on ethyl chloroformate.
Ethyl carbamate has been used as an antineoplastic agent and for other medicinal purposes, but this application ended after it was discovered to be carcinogenic in 1943. However, Japanese usage in medical injections continued and from 1950 to 1975 an estimated 100 million 2 ml ampules of 7-to-15% solutions of ethyl carbamate were injected into patients as a co-solvent in water for dissolving water-insoluble analgesics used for post-operation pain. These doses were estimated to be at levels that are carcinogenic in mice. This practice was stopped in 1975. "This regrettable medical situation appears to have involved the largest number (millions) of humans exposed to the largest doses of a pure carcinogen that is on record". The author, U.S. cancer researcher James A. Miller, called for studies to determine the effects on Japanese cancer rates to be performed but apparently none were ever done.[citation needed]
Prior to World War II, ethyl carbamate saw relatively heavy use in the treatment of multiple myeloma before it was found to be toxic, carcinogenic, and largely ineffective. By US FDA regulations, ethyl carbamate has been withdrawn from pharmaceutical use. However, small quantities of ethyl carbamate are also used in laboratories as an anesthetic for animals.
Ethyl carbamate was reclassified as a Group 2A carcinogen by IARC in 2007.
Ethyl carbamate is used as an anaesthetic in animal experiments, with more than 100 animal studies using ethyl carbamate published each year. One advantage of using ethyl carbamate is that it has a very long duration of action, with some adult rats remaining anaesthetised 24 hours after administration of the drug. It also does not depress neuronal activity in the cortex to the same extent as isoflurane.
Formerly, ethyl carbamate was used as a chemical intermediate in the preparation of amino resins, that were in turn used as crosslinking agents for permanent-press textile treatments to create "wash-and-wear" fabrics. Other uses included as solvent or intermediary in the manufacture of pesticides, cosmetics and pharmaceuticals.
The widespread presence of ethyl carbamate in alcoholic beverages was discovered during the mid-1980s. To raise public awareness of this issue, the U.S. Center for Science in the Public Interest published, in 1987, Tainted Booze: The Consumer's Guide to Urethane in Alcoholic Beverages. Studies have shown that most, if not all, yeast-fermented alcoholic beverages contain traces of ethyl carbamate (15 ppb to 12 ppm). Other foods and beverages prepared by means of fermentation also contain ethyl carbamate. For example, bread has been found to contain 2 ppb; as much as 20 ppb has been found in some samples of soy sauce. Amounts of both ethyl carbamate and methyl carbamate have also been found in wines, sake, beer, brandy, whiskey and other fermented alcoholic beverages.
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