D09 (medicated dressing)
|Jmol-3D images||Image 1|
|Molar mass||289.54 g mol−1|
120 °C, 393 K, 248 °F
|Flash point||162.2 °C (324.0 °F)|
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Triclosan is an antibacterial and antifungal agent. It is a polychloro phenoxy phenol. Though many products contain triclosan, there is no evidence according to the Food and Drug Administration (FDA) that triclosan provides an extra benefit to health beyond its anti-gingivitis effect in toothpaste. However, studies by the Environmental Protection Agency (EPA) found triclosan to be an effective antibacterial. Triclosan safety is currently under review by the FDA and Health Canada.
Chemical structure and properties 
This organic compound is a white powdered solid with a slight aromatic/phenolic odor. It is a chlorinated aromatic compound that has functional groups representative of both ethers and phenols. Phenols often show antibacterial properties. Triclosan is only slightly soluble in water, but soluble in ethanol, methanol, diethyl ether, and strongly basic solutions such as a 1 M sodium hydroxide solution. Triclosan can be synthesized from 2,4-dichlorophenol.
Some common impurities are: 2,4-dichlorophenol, 3-chlorophenol, 4-chlorophenol, 2,3,7,8-tetrachlorodibenzo-p-dioxin, 2,3,7,8-tetrachlorodibenzo-p-furan, 2,8-dichlorobenzo-furan, 2,8-dichlorobenzo-p-dioxin, 1,3,7-trichlorodibenzo-p-dioxin and 2,4,8-trichlorodibenzo-furan
2,4,4'-trichloro-2'-methoxydiphenyl ether is treated with aluminium chloride in benzene under reflux.
Triclosan can be synthesized through a three-step process starting with 1-(2-hydroxyethyl)pyrrolidin-2-one. The 1-(2-hydroxyethyl)pyrrolidin-2-one is to be dehydrated with either zinc or calcium oxide into 1-vinylpyrrolidin-2-one. Then, 1-vinylpyrrolidin-2-one can be reacted with 5-chloro-2-(2,4-dichlorophenoxy)phenyl acrylate in n-heptane to form triclosan.
It can be used to produce 2-(2,4-dichloro-phenoxy)-4,5-dichloro-phenol at 20 °C with the reagent sulfuryl chloride.
Triclosan has been used since 1972, and it is present in soaps (0.10-1.00%), deodorants, toothpastes, mouth washes, and cleaning supplies, and is infused in an increasing number of consumer products, such as kitchen utensils, toys, bedding, socks, and trash bags. Triclosan has been shown to be effective in reducing and controlling bacterial contamination on the hands and on treated products. More recently, showering or bathing with 2% triclosan has become a recommended regimen in surgical units for the decolonization of patients whose skin is carrying methicillin-resistant Staphylococcus aureus (MRSA) following the successful control of MRSA outbreaks in several clinical settings. Use in surgical units is effective with a minimum contact time of approximately 2 minutes.
Triclosan is regulated by the U.S. Food and Drug Administration, the Environmental Protection Agency, and the European Union. During wastewater treatment, a portion of triclosan is degraded, while the remaining adsorbs to sewage sludge or exits the plant in wastewater effluent. In the environment, triclosan may be degraded by microorganisms or react with sunlight, forming other compounds, which include between 3 and 12% of chlorophenols and dioxin (In particular, 2,8-dichlorodibenzo-p-dioxin (external) (2,8-DCDD) and 2,4-dichlorophenol (2,4-DCP) are produced. Both also are photolabile and, thus, are intermediates.), or it may adsorb to particles that settle out of the water column and form sediment. Triclosan was found in Greifensee sediment that was over 30 years old, suggesting that triclosan is degraded or removed slowly in sediment.
Triclosan also has been employed as an effective selective agent in molecular cloning. Bacteria host transformed by plasmids harboring a triclosan resistant mutant FabI gene (mFabI) as a selectable marker can grow in presence of high dose of triclosan in the culture media. 
Mechanism of action 
At in-use concentrations, triclosan acts as a biocide, with multiple cytoplasmic and membrane targets. At lower concentrations, however, triclosan appears bacteriostatic and is seen to target bacteria mainly by inhibiting fatty acid synthesis. Triclosan binds to bacterial enoyl-acyl carrier protein reductase enzyme (ENR), which is encoded by the gene FabI. This binding increases the enzyme's affinity for nicotinamide adenine dinucleotide (NAD+). This results in the formation of a stable ternary complex of ENR-NAD+-triclosan, which is unable to participate in fatty acid synthesis. Fatty acids are necessary for reproducing and building cell membranes. Humans do not have an ENR enzyme, and thus are not affected. Some bacterial species can develop low-level resistance to triclosan at its lower bacteriostatic concentrations because of FabI mutations, which results in a decrease of triclosan's effect on ENR-NAD+ binding, as shown in Escherichia coli and Staphylococcus aureus. Another way for these bacteria to gain low-level resistance to triclosan is to overexpress FabI. Some bacteria have innate resistance to triclosan at low, bacteriostatic levels, such as Pseudomonas aeruginosa, which possesses multi-drug efflux pumps that "pump" triclosan out of the cell. Other bacteria, such as some of the Bacillus genus, have alternative FabI genes (FabK) to which triclosan does not bind and hence are less susceptible.
Formation of dioxin in surface water 
The use of triclosan in household antibacterial products introduces the chemical to surface waters where it can degrade to a non-toxic type of dioxin. The dioxin-like compound that formed when triclosan degraded in sunlight and wastewater chlorine treatment were analyzed in sediment cores by University of Minnesota researchers.
Resistance concerns 
An article coauthored by Stuart Levy in the August 6, 1998 issue of Nature warned that triclosan's overuse could cause resistant strains of bacteria to develop, in much the same way that antibiotic-resistant bacterial strains are emerging. In 2003, the Scottish Sunday Herald newspaper reported that some UK supermarkets and other retailers were considering phasing out products containing triclosan.
It has since been shown that while the laboratory method used by Levy was not effective in predicting bacterial resistance for biocides like triclosan, triclosan does reduce species diversity, kills off efficient TCS degrader species (see citation's Table 4), and that it should be considered that "degradation of an ecosystem may rearrange the competitive hierarchy". At least seven peer-reviewed and published studies have been conducted demonstrating that triclosan is not significantly associated with bacterial resistance over the short term, including one study coauthored by Levy. However, the major concern over resistant strains is not that they will alter resistance profiles over the short term. The concern is that superbugs will evolve against which no bactericide can be used. For example, as noted above, triclosan is effective against MRSA. However, overuse of triclosan could lead to MRSA that is also triclosan-resistant.
Some level of triclosan resistance can occur in some microorganisms, but the larger concern is with the potential for cross-resistance or co-resistance to other antimicrobials. Studies investigating this possibility have been limited. The European Commission Scientific Committee on Consumer Safety (SCCS) concludes that to date, there is no evidence that using triclosan leads to an increase in antibiotic resistance. However it is too early to say that triclosan exposure never leads to microbial resistance, as there is not yet enough information to make a full risk analysis.
Health concerns 
Triclosan is used in a variety of common household products, including soaps, mouthwashes, dish detergents, toothpastes, deodorants, and hand sanitizers. In the United States, manufacturers of products containing triclosan must indicate it on the label.
Triclosan is a chlorinated aromatic compound with antibacterial, antifungal and antiviral properties (sold under several trade names, including UltraFresh, Amicor, and BioFresh). Triclosan is also a component in some pesticides, mattresses, insulation, and underlayments that install under various types of flooring, including laminate, wood, glued down, and engineered wood, and carpeting for the purpose of slowing or stopping the growth of bacteria, fungi, and mildew. For example, some high density sound-suppressing underlayments, foam floor underlayments and rebond carpet pads are treated with triclosan. Triclosan penetrates the skin on contact and enters the bloodstream  .
A 2010 study found that children who had higher exposure to triclosan had more hay fever. This may be because exposure to bacteria reduces allergies, as predicted by the hygiene hypothesis and not toxicology of the triclosan itself. This would also occur with chlorhexidine gluconate and PCMX, among other antibacterial agents. Other studies have linked triclosan to allergic contact dermatitis in some individuals.
In August 2009, the Canadian Medical Association asked the Canadian government to ban triclosan use in household products under concerns of creating bacterial resistance and producing dangerous side products (chloroform).
Triclosan also reacts with the free chlorine in tap water to produce lesser amounts of other compounds, like 2,4-dichlorophenol. Most of these intermediates convert into dioxins upon exposure to UV radiation (from the sun or other sources). Although small amounts of dioxins are produced, some dioxins are extremely toxic and are very potent endocrine disruptors. They are also chemically stable, so that they are eliminated from the body slowly (they can bioaccumulate to dangerous levels), and they persist in the environment for a long time.
Triclosan is chemically somewhat[ambiguous] similar to the dioxin class of compounds. Its production leads to small amounts of residual polychlorinated dioxins, and polychlorinated furans in the products that are produced with it.
Endocrine disruption 
A 2006 study concluded that low doses of triclosan act as an endocrine disruptor in the North American bullfrog. The hypothesis proposed is that triclosan blocks the metabolism of thyroid hormone because it chemically mimics thyroid hormone and binds to the hormone receptor sites, blocking them, so that normal hormones cannot be used. A study between 2003 and 2006 concluded that triclosan (as an endocrine disruptor) affects the immune system and showed a positive association with allergy or hay fever diagnosis. Another study in 2000 offered the result that low amount of triclosan can be absorbed through skin and can enter the bloodstream.
Triclosan has also been found in both the bile of fish living downstream from waste-water-processing plants and in human milk. The negative effects of triclosan on the environment and its questionable benefits in toothpastes have led to the Swedish Naturskyddsföreningen to recommend not using triclosan in toothpaste. Another 2009 study demonstrated that triclosan exposure significantly impacts thyroid hormone concentrations in the male juvenile rats.
Triclosan is also showing up in dolphins near South Carolina and Florida in concentrations known to disrupt hormones, growth, and development in other animals.
However, a 4-year study of possible effects of triclosan (0.3%) in toothpaste on thyroid hormone function found no effect of triclosan on thyroid hormone concentration in sera of adult human subjects. 
Muscle contraction 
Possible breakdown into carcinogenic metabolite 
Two reports by the same authors suggest that triclosan can combine with chlorine in tap water to form chloroform[not in citation given], which the United States Environmental Protection Agency classifies as a probable human carcinogen, meaning it likely causes cancer. These intermediates can be cleaved to form chlorophenols that can react with free chlorine to form trihalomethanes, such as chloroform. As a result, triclosan was the target of a UK cancer alert, even though the study showed that the amount of chloroform generated was less than amounts often present in chlorinated drinking water.
A comprehensive analysis from the University of Michigan School of Public Health indicated that plain soaps are just as effective as consumer-grade antibacterial soaps with triclosan in preventing illness and removing bacteria from the hands.
See also 
- Chlorhexidine gluconate
- Hygiene hypothesis
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