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Dextromethorphan

Dextromethorphan

Dextromethorphan hydrobromide monohydrate (DM or DXM) is an antitussive drug that is found in many over-the-counter cold and cough preparations. It is a salt of the methyl ether dextrorotatory isomer of levorphanol, a narcotic analgesic. It is chemically named as 3-methoxy-17-methyl-9(alpha), 13(alpha), 14(alpha)-morphinan hydrobromide monohydrate. DXM occurs as white crystals, is sparingly soluble in water, and freely soluble in alcohol. The drug is dextrorotatory in water (at 20 degrees Celsius, Sodium D-line) with a specific rotation of +27.6 degrees.

Indications

The FDA approved dextromethorphan for over-the-counter sale as an antitussive in 1958. This filled the need for a cough suppresant lacking the abuse liability and addictive properties of codeine phosphate, the most widely used cough medication at the time. The advantage of dextromethorphan preparations over those containing codeine (now controlled by the FDA) was the lack of physical addiction potential and sedative side-effects.

Pharmacodynamics

At therapeutic doses, the drug acts centrally to elevate the threshold for coughing, without inhibiting ciliary activity. DXM is rapidly absorbed from the gastrointestinal tract, and exerts its activity within 15 to 60 minutes of ingestion. The duration of action after oral administration is approximately three to six hours. DXM is metabolized by various liver enzymes and subsequently undergoes O-demethylation, N-demethylation, and partial conjugation with glucuronic acid and sulfate ions. Hours after DXM therapy, (in humans) the metabolites (+)-3-hydroxy-N-methylmorphinan, (+)-3-morphinan, and traces of the unchanged drug are detectable in the urine. Because administration of DXM can be accompanied by histamine release, its use in atopic children is very limited. The average dosage necessary for effective antitussive therapy is between 10mg and 30mg every four to six hours. According to the WHO committee on Drug Dependence, DXM, when used recreationally (see non-medical use of dextromethorphan), doesn't produce physical addiction but can generate slight psychological dependence in some users.

Clinical pharmacology

Following oral administration, DXM is rapidly absorbed from the gastrointestinal tract, where it enters the bloodstream and crosses the blood-brain barrier. The first-pass through the hepatic portal vein results in some of the drug being metabolized into an active metabolite of dextromethorphan, dextrorphan, the 3-hydroxy derivative of dextromethorphan. The therapeutic activity of dextromethorphan is believed to be caused by both the drug and this metabolite. Dextromethorphan is predominantly metabolized by the liver, by various hepatic enzymes. Through various pathways, the drug undergoes (O-demethylation (which produces dextrorphan), N-demethylation, and partial conjugation with glucuronic acid and sulfate ions. The inactive metabolite (+)-3-hydroxy-N-methylmorphinan is formed as a product of DXM metabolism by these pathways. One well known metabolic catalyst involved is a specific cytochrome P450 enzyme known as 2D6, or CYP2D6. A significant portion of the population has a functional deficiency in this enzyme (and are known as poor CYP2D6 metabolizers). As CYP2D6 is the primary metabolic pathway in the inactivation of dextromethorphan, the duration of action and effects of dextromethorphan are significantly increased in such poor metabolizers. Deaths and hospitalizations have been reported in recreational use by poor metabolizers of CYP2D6. A large number of medications (including antidepressants) are potent inhibitors of CYP2D6 (see CYP2D6 article). There exists, therefore, the potential of drug-drug interactions between dextromethorphan and concomitant medications. There have been reports of fatal consequences arising from such interactions. Dextromethorphan crosses the blood-brain barrier, and the following pharmacological actions have been reported:
- NMDA glutamatergic receptor antagonist
- Dopamine reuptake inhibitor
- σ₁ and σ₂ receptor agonist (Zhou & Musacchio, 1991)
- α3β4 nicotinic receptor antagonist [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10869398]
- Serotonin reuptake inhibitor [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=1636059]

History

Dextromethorphan was first patented with , and was approved for over-the-counter sale as an antitussive in 1958.

Antitussive

A cough medicine is a drug used to treat coughing and related conditions. Dry coughs are treated with cough suppressants (antitussives) that suppress the body's urge to cough, while productive coughs (coughs that produce phlegm) are treated with expectorants that loosen mucus from the respiratory tract.

Cough suppressants

Cough suppressants may act centrally (on the brain) or locally (on the respiratory tract) to suppress the cough reflex. Centrally acting suppressants include dextromethorphan (DXM), noscapine, ethyl morphine, and codeine. Peripherally acting substances include local anaesthetics, which reduce the sensation of nerves in the throat, and demulcents, which coat the esophagus. Although it is commonly believed that cough medicines must coat the throat to be effective, there is no evidence that it is possible to control coughing by this means. One might think it unwise to suppress the cough reflex (the mechanism for expelling mucus from the respiratory tract) but severe coughing may lead to lung irritation, causing a vicious cycle. The cough reflex is also very strong and cannot be completely suppressed. However, dry cough (without mucus production) or cough that is exhausting and preventing sleep should be treated with supressants. Recent studies have found that theobromine, a compound found in cocoa, is more effective as a cough suppressant than prescription codeine. This molecule suppresses the "itch" signal from the nerve in the back of the throat that causes the cough reflex. It is possible to get an effective dose from dark chocolate, which contains more cocoa than milk chocolate. Theobromine was also free from side effects in the blind tests.

Expectorants

An expectorant is a medicine or herb which increases the expulsion of tracheal or bronchial mucus through expectoration or coughing. In over-the-counter preparations, guaifenesin is often used. Herbal expectorants include the following:
- Aniseed (Pimpinella anisum),
- Balm of Gilead (Populus gileadensis),
- Balsam of Peru (Myroxylon perierae),
- Balsam of Tolu (Myroxylon toluifera),
- Blood Root (Sanguinaria canadensis),
- Coltsfoot (Tussilago farfara),
- Comfrey (Symphytum officinale),
- Elder Flower (Sambucus nigra),
- Elecampane (Inula helenium),
- Garlic (Allium sativum),
- Golden Seal (Hydrastis canadensis),
- Grindelia (Grindelia camporum),
- Hyssop (Hyssopus officinalis),
- Iceland Moss (Cetraria islandica),
- Irish Moss (Chondrus crispus),
- Liquorice (Glycyrrhiza glabra),
- Lobelia (Lobelia inflata),
- Lungwort (Sticta pulmonaria),
- Marshmallow (Althaea officinalis),
- Mouse Ear (Hieracium pilosella),
- Mullein (Verbascum thapsus),
- Pleurisy Root (Asclepias tuberosa),
- Senega (Polygala senega),
- Skunk Cabbage (Symplocarpus foetidus),
- Squill (Urginea maritima),
- Thuja (Thuja occidentalis),
- Thyme (Thymus vulgaris),
- Vervain (Verbena officinalis),
- White Horehound (Marrubium vulgare),
- Wild Cherry (Prunus serotona).

Cough drops

Cough drops are tablets which people can suck to soothe the throat or to alleviate excessive coughing. They are usually relatively small, sweetened, and contain medicine that helps to reduce pain or irritation. The occasional use of "lozenge" (first used in 1530, according to the Oxford English Dictionary) is due to the original lozenge shape of cough drops. Popular brands of cough drops include Fisherman's Friend, Halls (cough drop), and Ricola.

Controversy

In 2002, researchers at the University of Bristol (Schroeder & Fahey) published a study in the British Medical Journal indicating that some cough medicines are no more effective than placebos. Many cough mixtures contain both an expectorants and a suppressants -- even though an expectorant requires the action of a cough to expel mucus. Many believe this supports the idea that cough supression is just a placebo effect. However, in practice the two active ingredients combine to provide less coughing, but more productive coughs.

Colloquial term usage

"Cough medicine" is also commonly used as a euphemism for whiskey and other strong alcoholic beverages, as in "Grandpa's old cough medicine".

References

- Schroeder K, Fahey T. Systematic review of randomised controlled trials of over the counter cough medicines for acute cough in adults. BMJ 2002;324:329-31. [http://bmj.bmjjournals.com/cgi/content/full/324/7333/329 Fulltext]. PMID 11834560.
- [http://www.newscientist.com/article.ns?id=dn6699 Chocolate as a cough suppressant.]
-

Drug

Drug may refer to:
- Medication
- Psychoactive drug
- substances used for recreational drug use
- substances used in drug abuse
- Hard and soft drugs
- A drug or demon in ancient Vedic Hinduism, from the Vedic Sanskrit root druh = "be hostile"
- The Drûg or Drúedain, a race of Men from Middle-earth in the fiction of J. R. R. Tolkien

Common cold

The common cold (also known as "acute nasopharyngitis") is a mild viral infectious disease of the nose and throat; the upper respiratory system. Symptoms include sneezing, sniffling, running/blocked nose (often these occur simultaneously, or one in each nostril); scratchy, sore, or phlegmy throat; coughing; headache; and tiredness. Colds typically last three to five days, with residual coughing lasting up to three weeks. As its name suggests, it is the most common of all human diseases, infecting subjects at an average rate of slightly over one infection per year per person. Infection rates greater than three infections per year per person are not uncommon in some populations. Children and their caretakers are at a higher risk, probably due to the high population density of schools and the fact that transmission to family members or caretakers is highly efficient. The common cold belongs to the upper respiratory tract infections. It is different from influenza, a more severe viral infection of the respiratory tract that shows the additional symptoms of rapidly rising fever, chills, and body and muscle aches. While the common cold itself is hardly life threatening, its complications, such as pneumonia, can very well be.

Pathology

The common cold is caused by numerous viruses (mainly rhinoviruses, coronaviruses, and also certain echoviruses, paramyxoviruses, and coxsackieviruses) infecting the upper respiratory system. Several hundred cold-causing viruses have been described, and a virus can mutate to survive, ensuring that any cure is still a long way off. The viruses are transmitted from person to person by droplets resulting from coughs or sneezes. The droplets or droplet nuclei are either inhaled directly, or transmitted from hand to hand via handshakes or objects such as door knobs, and then introduced to the nasal passages when the hand touches the nose or eyes. The virus enters the cells of the lining of the nasopharynx (the area between the nose and throat), and rapidly multiplies. The major entry points are the nose and eyes, through the nasolacrymal duct drainage into the nasopharynx. The mouth is not a major point of entry and transmission does not usually occur with kissing or swallowing. The nasopharynx is the central area infected. The reasons that the virus concentrates in the nasopharynx rather than the throat may be the low temperature and high concentration of cells with receptors needed by the virus. The virus enters the cell by binding to ICAM-1 receptors in these cells. The presence of ICAM-1 affects whether a cell will be infected. Its concentration also can be affected by various other factors, including allergic rhinitis and some other irritants including rhinoviruses themselves. ICAM-1 has been a major focal point in drug research into cold treatments.

"Cold" as misnomer

The term "cold" (as it relates to climatic temperature) is somewhat misleading. Climate may affect transmission by some means, such as by causing people to stay indoors and increasing the proximity to infected persons, but the cause of the infection remains primarily viral. Some allergies, bacterial respiratory infections, and even climate changes can also cause common-cold-like symptoms that can last for days. It is not definitely known whether cold weather or a humid climate can affect transmission by other means, such as by affecting the immune system, or ICAM-1 receptor concentration, or simply increasing the amount and frequency of nasal secretions and frequency of hand to face contact. A person can best avoid colds by avoiding those who are ill and objects that they touch, as well as keeping their immune system in top form by getting enough sleep, reducing stress, eating nutritious foods, and avoiding excess alcohol consumption. It is perhaps the case that "cold" refers to a "cold condition;" i.e., the hot, cold, dry, and wet "conditions" described by the ancient Roman physician Galen. Colds are somewhat more common in winter since during that time of the year people spend more time indoors in close proximity to others, and ventilation is less efficient, increasing the infection risk. However, researchers at the University of Cardiff have recently shown that cold temperatures can lead to a greater chance of symptoms developing. They showed that a group of people who sat with their feet in cold water for 20 minutes a day for a week had a 1 in 3 chance of developing symptoms during that week, while a control group who sat with their feet in an empty bowl had a 1 in 10 chance. It is thought this may be due to cold temperatures reducing blood circulation, needed to carry white blood cells to the area of infection.

Symptoms

Ninety-five percent of people exposed to a cold virus become infected, although only 75% show symptoms. The symptoms start 1-2 days after infection. They are a result of the body's defense mechanisms: sneezes, runny nose, and coughs to expel the invader, and inflammation to attract and activate immune cells. The virus takes advantage of sneezes and coughs to infect the next person before it is killed by the body's immune system. Sneezes expel a significantly larger concentration of virus "cloud" than coughing. The "cloud" is partly invisible and falls at a rate slow enough to last for hours--with part of the water droplets evaporating and leaving much smaller and invisible "droplet nuclei" in the air. Droplets from turbulent sneezing or coughing or hand contact also can last for hours on surfaces, although less virus can be recovered from porous surfaces such as wood or paper towel than non-porous surfaces such as a metal bar. A sufferer is most infectious within the first three days of the illness. Symptoms, however, are not necessary for viral shedding or transmission, as a percentage of asymptomatic subjects exhibit viruses in nasal swabs, likely controlling the virus at concentrations too low for them to have symptoms. After a common cold, a sufferer develops immunity to the particular virus encountered. However, because of the large number of different cold viruses, this immunity is of limited use. A person can therefore easily be infected by another cold virus to start the process all over again.

Complications

Bacteria that are normally present in the respiratory tract can take advantage of the weakened immune system during a common cold and produce a co-infection. Middle ear infection (in children) and bacterial sinusitis are common coinfections. A possible explanation for these coinfections is that strong blowing of the nose drives nasal fluids into those areas. The best way to blow the nose is keeping both nasal openings open when blowing and wiping rather than fully covering them, permitting pressure to partially dissipate. Doing so will reduce the pressure that would otherwise drive fluid into the ears or sinuses.

Prevention

The best way to avoid a cold is to avoid close contact with existing sufferers, to wash hands thoroughly and regularly, and to avoid touching the face. Anti-bacterial soaps have no effect on the cold virus - it is the mechanical action of hand washing that removes the virus particles. In 2002, the Centers for Disease Control and Prevention recommended alcohol based hand gels as an effective method for reducing infectious viruses on the hands. However, as with standard handwashing, alcohol gels provide no residual protection from re-infection. In some countries, such as China and Japan, people with the common cold wear surgical masks out of courtesy to protect others. Smoking has also been linked with the weakening of the immune system, non-smokers are known on average to take fewer days off sick than the smoking population. Smokers on average take 25% more sick days a year. Because of the large variety of viruses causing the common cold, vaccination is impractical.

Treatment

There is no cure for the common cold, i.e. there is no treatment that directly fights the virus. Only the body's immune system can effectively destroy the invader. A cold may be composed of several million viral particles, and typically within a few days the body begins mass producing a better tailored antibody that can prevent the virus from infecting cells, as well as white blood cells which destroy the virus through phagocytosis and destroy infected cells to prevent further viral replication. Furthermore the duration of infection is on the order of a few days to one week so at most a "cure" could hope to reduce the duration by only a few days. Available treatments therefore focus on relieving the symptoms. For some people, even without these remedies, colds are relatively minor inconveniences and they can go on with their daily activities with tolerable discomfort. This discomfort has to be weighed against the price and possible side effects of the remedies, and the possibility, not yet scientifically proven, that by suppressing responses evolved to fight the cold, the symptom suppressants may prolong the illness. Common treatments include: analgesics such as aspirin or acetaminophen, as well as localised versions targeting the throat (often delivered in lozenge form), nasal decongestants which reduce the inflammation in the nasal passages by constricting local blood vessels, cough suppressants (which work to suppress the cough reflex of the brain or by diluting the mucus in the lungs), and first-generation anti-histamines such as brompheniramine, chlorpheniramine, and clemastine (which reduce mucus gland secretion and thus combat blocked/runny noses but also may make the user drowsy). Second generation anti-histamines do not have a useful effect on colds. A warm and humid environment and drinking lots of fluids, especially hot liquids, alleviate symptoms somewhat. Common home remedies include camomile or lemon tisanes and chicken soup (which probably work by soothing the irritated respiratory passages with their steam), nebulized medicinal mixtures, hot compresses, mustard plasters, hot toddies, licorice and echinacea. Although there have been scientific studies done on echinacea, its effectiveness has not been demonstrated. Eating very spicy food can help alleviate congestion, although it may also irritate the already-tender throat. Coffee, or its active component, caffeine, has also been shown to improve mood and mental performance during rhinovirus infection. Hot beer is also recommended, and though it probably does little to fight the infection directly, at least it can help to a good night of relaxed sleep. However, alcohol dehydrates the body which is counterproductive; also cold medicine (aspirin, acetaminophen, ibuprofen, etc) should never be taken along with alcohol. Publications in the 1960s and 1970s suggested that large doses of Vitamin C could both prevent and reduce the effects of the common cold. A particularly vociferous proponent of this theory was Nobel Prize winner Linus Pauling, who heavily advocated the intake of large doses of Vitamin C to prevent infection. In 1970 he wrote the bestseller Vitamin C and the Common Cold. However, most physicians feel that large maintenance doses of Vitamin C do not lower the incidence of colds, and evidence has been conflicting as to whether or not vitamin C will shorten the duration of symptoms of any colds that occur. A meta-analysis published in 2005 found no support that vitamin C is of any benefit in the common cold. Zinc-containing preparates have been claimed to be effective in the treatment of cold infections. Some studies have attributed this to a placebo effect related to the strong and unpleasant taste of zinc preparates (Reference: [http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=174900&action=stream&blobtype=pdf Farr et al. (1987)]), while other studies claim that zinc lozenges are effective in reducing the duration and severity of common colds. (Reference: [http://coldcure.com/html/prasad.pdf]) Advocates for Zinc nasal sprays, however, claim clinical proof that they work. The trick seems to be threefold. One, the treatment has to be a nasal spray. Two, treatment should be started at the first sign of a cold before it has the chance to get established. Three, the type of zinc must be zinc gluconate usually labelled as zincum gluconicum. There have been several hundred lawsuits filed alleging that zinc nasal sprays may cause permanent damage to the sense of smell. Antibiotics are ineffective against the common cold and all other viral infections. They are useful in treating any secondary bacterial infections that sometimes occur, but treatment with antibiotics before these coinfections develop is counterproductive, as it produces drug resistance, and can even promote infections by killing off normal bodily flora.

Societal impact

Common colds interfere with school attendance and can cause lost days on the job, resulting in considerable costs to the economy. In addition, much money is spent on over-the-counter and home remedies. Arguably the most common disorder that humans can be afflicted with, the cold is considered something of a common cultural point of reference. Thus, catching a cold is often used as a plot device in various stories, movies, and television series. Some companies have begun to offer a number of paid sick days per year to avoid errors during work and transmission to coworkers. U. of Michigan resesarcher Dr. A. Mark Fendrick published 2003 study on effects of the common cold: The study found that the common cold leads to more than 100 million physician visits annually at a conservative cost estimate of $7.7 billion per year. More than one-third of patients who saw a doctor received an antibiotic prescription, which Fendrick says not only contributes to unnecessary costs, but also has implications for antibiotic resistance from overuse of such drugs. The study found that Americans spend $2.9 billion on over-the-counter drugs and another $400 million on prescription medicines for symptomatic relief. Additionally, cold sufferers spend $1.1 billion annually on an estimated 41 million antibiotic prescriptions, even though the drugs have no effect on a viral illness. The study reports that an estimated 189 million school days are missed annually due to a cold. As a result, parents missed 126 million workdays to stay home to care for their children. When added to the workdays missed by employees suffering from a cold, the total economic impact of cold-related work loss exceeds $20 billion."

History

Colds were known in ancient Egypt; there were hieroglyphs for cough and for the common cold. The Greek Hippocrates gave a description of the disease in the 5th century BC. The common cold was also known in the ancient American Indian Aztec and Maya civilizations. A mixture of chili pepper, honey, and tobacco was one common Aztec treatment for colds. In the 18th century, John Wesley wrote a book about curing diseases; it advised cold baths as prevention and stated that chilling causes the common cold. The work was widely reprinted in the 19th century. Another book by William Buchan in the 18th century also gave wet feet and clothes as the cause of the common cold. The idea of microscopic infectious agents causing disease arose in the second half of the 19th century. Initially, bacteria were suspected to be the cause of the common cold, and vaccines were produced based on this theory; these were still prescribed in the 1950s. Viruses had been described beginning with the 1890s: infectious agents so small that they could pass through all filters and could not be seen under a microscope. In 1914, Walter Kruse, a professor in Leipzig, Germany, showed that viruses caused the common cold: nose secretions of a cold sufferer were diluted, filtered, and introduced into the noses of volunteers, producing colds in about half of the cases. These findings were not widely accepted, until they were repeated in the 1920s by Alphonse Dochez, first in chimpanzees, and then in human volunteers using a proper double-blind setup. Yet in 1932 a major textbook on the common cold by David Thomson still presented bacteria as the most likely cause. Among laymen, the common assumption that cold or wet clothes or feet cause the common cold persists to this day. In Britain, the Common Cold Unit was set up by the civilian Medical Research Council in 1946. The unit worked with volunteers who were infected with various viruses. The rhinoviruses were discovered there. In the late 1950s, it was shown how to grow one of these cold viruses in tissue culture (it would not grow in fertilized chicken eggs, the method used for many other viruses). In the 1970s, it was also shown that treatment with interferon during the incubation phase of rhinovirus infection protects somewhat against the disease, but no practical treatment could be developed. The unit was closed in 1989.

Note

- Douglas RM, Hemilä H. Vitamin C for Preventing and Treating the Common Cold. PLoS Med 2005;2(6):e168.

External links

- [http://www.commoncold.org/ Commoncold.org] edited by MDs
- [http://www.nlm.nih.gov/medlineplus/commoncold.html Common Cold] Links to health information from MedlinePlus
- [http://www.kcom.edu/faculty/chamberlain/Website/lectures/lecture/uri.htm Common Cold syllabus] from Infectious Diseases, Medical Microbiology, by Neal Chamberlain, PhD. Kirksville College of Osteopathic Medicine
- [http://www.consumerreports.org/main/content/display_report.jsp?FOLDER%3C%3Efolder_id=377601&bmUID=1101139924451 Do I have a Cold or the Flu?] from ConsumerReports.org
- [http://www.findarticles.com/p/articles/mi_qn4196/is_20030317/ai_n10850727 "Falling ill to a chill"] (Milwaukee Journal Sentinel, 17 Mar 2003)
- [http://www.merck.com/pubs/mmanual/section13/chapter162/162b.htm Merck Manual on Respiratory Viral Diseases: Common cold]
- [http://www.verrueckte-experimente.de/leseproben_e.html#story_08 The first common cold experiments (1946)] with film clip
- [http://fampra.oxfordjournals.org/cgi/content/abstract/cmi072v1 Acute cooling of the feet and the onset of common cold symptoms Johnson and Eccles Fam. Pract..2005; 0: 721]

Cough syrup

Cough suppressants

Expectorants

Cough drops

Controversy

Colloquial term usage

"Cough medicine" is also commonly used as a euphemism for whiskey and other strong alcoholic beverages, as in "Grandpa's old cough medicine".

References

Salt

: This article is about the general chemical term salt. For the everyday meaning, see edible salt or its main ingredient, sodium chloride. For other meanings of the word salt, see salt (disambiguation). In chemistry, salt is a term used for ionic compounds composed of positively charged cations and negatively charged anions, so that the product is neutral and without a net charge. These ions can be inorganic (Cl^-) as well as organic (CH₃-COO^-) and monoatomic (F^-) as well as polyatomic ions (SO₄^2-). Solutions of salts in water are called electrolytes. Electrolytes as well as molten salts conduct electricity. Zwitterions are salts that contain an anionic center and a cationic center in the same molecule, examples are the amino acids, many metabolites, peptides, and proteins. Mixtures of many different ions in solution like in the cytoplasm of cells, in blood, urine, plant saps, and mineral waters usually do not form defined salts after evaporation of the water. Therefore their salt content is given for the respective ions. Impure salt is a name for salt which has lost its saltiness. It can also refer to natron.

Appearance

Consistency

Salts are usually solid crystals with a relatively high melting point. However, there exist salts that are liquid at room temperature, so-called ionic liquids. Inorganic salts usually have a low hardness and a low compressibility, similar to edible salt.

Color

Salts can be clear and transparent (sodium chloride), opaque (titanium dioxide), and even metallic and lustrous (iron disulfide). Salts exist in all different colors, e.g. yellow (sodium chromate), orange (sodium dichromate), red (mercury sulfide), mauve (cobalt dichloride hexahydrate), blue (copper sulfate pentahydrate, ferric hexacyanoferrate), green (nickel oxide), colorless (magnesium sulfate), white (titanium dioxide), and black (manganese dioxide). Most minerals and inorganic pigments as well as many synthetic organic dyes are salts.

Taste

Different salts can elicit all five basic tastes, i.e. salty (sodium chloride), sweet (lead diacetate), sour (potassium bitartrate), bitter (magnesium sulfate), and umami or savory (monosodium glutamate).

Odor

Pure salts are odorless, while impure salts may smell after the acid (e.g. acetates like acetic acid (vinegar), cyanides like hydrogen cyanide (almonds)) or the base (e.g. ammonium salts like ammonia).

Nomenclature

The name of a salt starts with the name of the cation (e.g. sodium or ammonium) followed by the name of the anion (e.g. chloride or acetate). Salts are often referred to only by the name of the cation (e.g. sodium salt or ammonium salt) or by the name of the anion (e.g. chloride or acetate). Common salt-forming cations are:
- ammonium NH₄⁺
- calcium Ca²⁺
- iron Fe²⁺ and Fe³⁺
- magnesium Mg²⁺
- potassium K⁺
- pyridinium C₅H₅NH⁺
- quaternary ammonium NR₄⁺
- sodium Na⁺ Common salt-forming anions (and the name of the parent acids in parentheses) are:
- acetate CH₃-COO^- (acetic acid)
- carbonate CO₃^2- (carbonic acid)
- chloride Cl^- (hydrochloric acid)
- citrate HO-C(COO^-)(CH₂-COO^-)₂ (citric acid)
- cyanide C≡N^- (hydrogen cyanide)
- hydroxide OH^- (water)
- nitrate NO₃^- (nitric acid)
- nitrite NO₂^- (nitrous acid)
- oxide O^2- (water)
- phosphate PO₄^3- (phosphoric acid)
- sulfate SO₄^2- (sulfuric acid)

Formation

Salts are formed by a chemical reaction between:
- a base and an acid, e.g. NH₃ + HCl → NH_{4_Cl}
- a metal and an acid, e.g. Mg + H₂SO₄ → MgSO₄ + H₂ Salts can also form if solutions of different salts are mixed, their ions recombine, and the new salt is insoluble and precipitates (see: Solubility equilibrium).

References

- Kurlansky, Mark (2002). Salt: A World History. Walker Publishing Company. ISBN: 0142001619
- silting is the natural deposit of salt from sea water

Isomer

:This article is about chemical isomers. For another use, see nuclear isomer. In chemistry, isomers are molecules with the same chemical formula and often with the same kinds of bonds between atoms, but in which the atoms are arranged differently. Many isomers share similar if not identical properties in most chemical contexts. A simple example of isomerism is given by propanol: it has the formula C₃H₈O (or C₃H₇OH) and the isomers Propan-1-ol (n-propyl alcohol; left) Propan-2-ol (isopropyl alcohol; right) H H H H H H | | | | | | H-C-C-C-O-H H-C-C-C-H | | | | | | H H H H O H | H Note that the position of the oxygen atom differs between the two: it is attached to an end carbon in the first isomer, and to the center carbon in the second. The number of possible isomers increases rapidly as the number of atoms increases; for example the next largest alcohol, named butanol (C₄H₁₀O), has five different isomers. In the example above it should also be noted that in both isomers all the bonds are single bonds; there is no type of bond that appears in one isomer and not in the other. Also the number of bonds is the same. From the structures of the two molecules it could be deduced that their chemical stabilities are liable to be identical or nearly so. There is, however, another isomer of C₃H₈O which has significantly different properties: methyl ethyl ether: H H H | | | H-C-C-O-C-H | | | H H H Notice that unlike the top two examples, the oxygen is connected to two carbons rather than to one carbon and one hydrogen. As it lacks a hydroxl group, the above molecule is no longer considered an alcohol but is classified as an ether, and has chemical properties more similar to other ethers than to either of the above alcohol isomers. Another example is the dimethylxanthines. Theobromine is found in chocolate, but if one of the two methyl groups is moved to a different position on the two-ring core, the isomer is theophylline, used as a bronchodilator.

History

Isomerism was first noticed in 1825, when Friedrich Woehler prepared cyanic acid and noted that although its elemental composition was identical to fulminic acid (prepared by Justus von Liebig the previous year), its properties were quite different. This finding challenged the prevailing chemical understanding of the time, which held that chemical compounds could be different only when they had different elemental compositions. After additional discoveries of the same sort were made, such as Woehler's 1828 discovery that urea had the same atomic composition as the chemically distinct ammonium cyanate, Berzelius introduced the term isomerism to describe the phenomenon. In 1849, Louis Pasteur separated tiny crystals of tartaric acid into their two mirror-image forms. The individual molecules of each were the left and right optical stereoisomers, solutions of which rotate the plane of polarized light in opposite directions.

Different forms of isomerism

light There are two main forms of isomerism: structural isomerism and stereoisomerism. In structural isomers, the atoms and functional groups are joined together in different ways, as in the example of propyl alcohol above. This group includes chain isomerism whereby hydrocarbon chains have variable amounts of branching; position isomerism which deals with the position of a functional group on a chain; and functional group isomerism in which one functional group is split up into different ones. In stereoisomers the bond structure is the same, but the geometrical positioning of atoms and functional groups in space differs. This class includes optical isomerism where different isomers are mirror-images of each other, and geometric isomerism where functional groups at the end of a chain can be twisted in different ways. While structural isomers typically have different chemical properties, stereoisomers behave identically in most chemical reactions. Enzymes however can distinguish between different stereoisomers of a compound, and organisms often prefer one stereoisomer over the other. Some stereoisomers also differ in the way they rotate polarized light. There also exist topological isomers called topoisomers. Molecules with topoisomers include catenanes and DNA. Topoisomerase enzymes can knot DNA and thus change its topology. There are also isotopomers or isotopic isomers that have the same numbers of each type of isotopic substitution but in chemically different positions. In nuclear physics, isomers are excited states of atomic nuclei; see nuclear isomer.

Analgesic

An analgesic (colloquially known as painkiller) is any member of the diverse group of drugs used to relieve pain and to achieve analgesia. This derives from Greek an-, "without", and -algia, "pain". Analgesic drugs act in various ways on the peripheral and central nervous system; they include paracetamol (acetaminophen), the nonsteroidal anti-inflammatory drugs (NSAIDs) such as the salicylates, narcotic drugs such as morphine, synthetic drugs with narcotic properties such as tramadol, and various others. Some other classes of drugs not normally considered analgesics are used to treat neuropathic pain syndromes; these include tricyclic antidepressants and anticonvulsants.

Stepwise use

In 1990, the World Health Organisation (WHO) approved an "analgesic ladder" which recommends the stepwise introduction of stronger painkillers if the more basic ones are ineffective. While originally introduced for managing pain in cancer, these guidelines have found application in all fields of medicine, such as surgery and anaesthetics. # The first step is paracetamol (500 mg to 1 g every 4-6 hours). # The second step involves the addition of an NSAID (e.g. ibuprofen) or a weak opioid (such as codeine). # The third step comprises the addition of a strong opioid (such as morphine, oxycodone or a fentanyl preparation); if codeine is being taken the strong opioid replaces codeine.

The major classes

Paracetamol and NSAIDs

The exact mechanism of action of paracetamol is uncertain, but it appears to be acting centrally. Aspirin and the NSAIDs inhibit cyclooxygenase, leading to a decrease in prostaglandin production; this improves pain and also inflammation (in contrast to paracetamol and the opioids). Paracetamol has few side effects, but dosing is limited by possible hepatotoxicity (potential for liver damage). NSAIDs may predispose to peptic ulcers, renal failure, allergic reactions, and hearing loss. They may also increase the risk of hemorrhage.

Opiates and morphinomimetics

Tramadol and buprenorphine are thought to be partial agonists of the opioid receptors. Morphine, the archetypical opioid, and various other substances (e.g. pethidine, oxycodone, hydrocodone, diamorphine) all exert a similar influence on the cerebral opioid system. Dosing may be limited by opioid toxicity (confusion, myoclonic jerks and pinpoint pupils), but there is no dose ceiling in patients who tolerate this. Opioids, while very effective analgesics, may have some unpleasant side-effects. Up to 1 in 3 patients starting morphine may experience nausea and vomiting (generally relieved by a short course of antiemetics). Pruritus (itching) may require switching to a different opioid. Constipation occurs in almost all patients on opioids, and laxatives (lactulose, macrogol-containing or co-danthramer) are typically co-prescribed. When used appropriately, opioids and similar narcotic analgesics are safe and effective, carrying relatively little risk of addiction. Occasionally, gradual tapering of the dose is required to avoid withdrawal symptoms.

Specific agents

In patients with chronic or neuropathic pain, various other substances may have analgesic properties. Tricyclic antidepressants, especially amitriptyline, have been shown to improve pain in what appears to be a central manner. The exact mechanism of carbamazepine, gabapentin and pregabalin is similarly unclear, but these anticonvulsants are used to treat neuropathic pain with modest success.

Specific forms and uses

Combinations

Analgesics are frequently used in combination, such as the paracetamol and codeine preparations found in many non-prescription pain relievers. They can also be found in combination with vasoconstrictor drugs such as pseudoephedrine for sinus-related preparations, or with antihistamine drugs for allergy sufferers.

Topical or systemic

Topical analgesia is generally recommended to avoid systemic side-effects. Painful joints, for example, may be treated with an ibuprofen- or diclofenac-containing gel; capsaicin also is used topically. Lidocaine and steroids may be injected into painful joints for longer-term pain relief. Lidocaine is also used for painful mouth sores and to numb areas for dental work and minor medical procedures.

Psychotropic agents

Tetrahydrocannabinol and some other cannabinoids, either from the Cannabis sativa plant or synthetic, have analgesic properties, although the use of cannabis derivatives is illegal in many countries. Other analgesic agents include ketamine (an NMDA receptor antagonist), clonidine and other α₂-adrenoreceptor agonists, and mexiletine and other local anaesthetic analogues.

Addiction

In the United States in recent years, however, there has been a wave of new addictions to prescription painkillers such as oxycodone (OxyContin, Percocet etc.) and hydrocodone (Vicodin, Lortab etc.). The U.S. Government is now taking steps to reverse this epidemic, which it has blamed on easy access to prescription drugs over the Internet.

Reference

- Cancer pain relief and palliative care. Report of a WHO expert committee [World Health Organization Technical Report Series, 804] . Geneva, Switzerland: World Health Organization; 1990. pp. 1-75. Category:Analgesics Category:Pain ms:Analgesik th:ยาบรรเทาปวด

Ethanol

Ethanol, also known as ethyl alcohol or grain alcohol, is a flammable, colorless chemical compound, one of the alcohols that is most often found in alcoholic beverages. In common parlance, it is often referred to simply as alcohol. Its chemical formula is C₂H₅OH, also written as C₂H₆O. This article is mostly about ethanol as a chemical compound. For beverages containing ethanol, see alcoholic beverage. For the use of ethanol as a fuel, see alcohol fuel.

History

Ethanol has been used by humans since prehistory as the intoxicating ingredient in alcoholic beverages. Dried residues on 9000-year-old pottery found in northern China imply the use of alcoholic beverages even among Neolithic peoples. Its isolation as a relatively pure compound was first achieved by Islamic alchemists who developed the art of distillation during the Abbasid caliphate. The writings of Jabir Ibn Hayyan (Geber) (721-815) mention the flammable vapors of boiled wine. Al-Kindī (801-873) unambiguously described the distillation of wine. Distillation of ethanol from water yields a product that is at most 96% ethanol. Absolute ethanol was first obtained in 1796 by Johann Tobias Lowitz, by filtering distilled ethanol through charcoal. Antoine Lavoisier described ethanol as a compound of carbon, hydrogen, and oxygen, and in 1808, Nicolas-Théodore de Saussure determined ethanol's chemical formula. In 1858, Archibald Scott Couper published a structural formula for ethanol: this places ethanol among the first chemical compounds to have their chemical structures determined. Ethanol was first prepared synthetically in 1826, through the independent efforts of Henry Hennel in Britain and S.G. Sérullas in France. Michael Faraday prepared ethanol by the acid-catalysed hydration of ethylene in 1828, in a process similar to that used for industrial ethanol synthesis today.

Production

ethylene Ethanol is produced both as a petrochemical, through the hydration of ethylene, and biologically, by fermenting sugars with yeast.

Ethylene hydration

Ethanol for use as industrial feedstock and is most often made from petroleum feedstocks, typically by the acid-catalysed hydration of ethylene, represented by the chemical equation : H₂C=CH₂ + H₂O → CH₃CH₂OH The catalyst is most commonly phosphoric acid, adsorbed onto a porous support such as diatomaceous earth or charcoal; this catalyst was first used for large-scale ethanol production by the Shell Oil Company in 1947. Solid catalysts, mostly various metal oxides, have also been mentioned in the chemical literature. In an older process, first practised on the industrial scale in 1930 by Union Carbide, but now almost entirely obsolete, ethylene was hydrated indirectly by reacting it with concentrated sulfuric acid to product ethyl sulfate, which was then hydrolyzed to yield ethanol and regenerate the sulfuric acid: : H₂C=CH₂ + H₂SO₄ → CH₃CH₂OSO₃H : CH₃CH₂OSO₃H + H₂O → CH₃CH₂OH + H₂SO₄ Ethanol for industrial use is normally made unfit for human consumption ("denatured") by the inclusion of small amounts of substances that are either toxic (such as methanol) or unpleasant (such as denatonium), thus avoiding the applicable taxes or inventory controls. Denatured ethanol has the UN number UN 1987 and toxic denatured ethanol has UN 1986.

Fermentation

Ethanol for use in alcoholic beverages, and the vast majority of ethanol for use as fuel, is produced by fermentation: when certain species of yeast (most importantly, Saccharomyces cerevisiae) metabolize sugar in the absence of oxygen, they produce ethanol and carbon dioxide. The overall chemical reaction conducted by the yeast may be represented by the chemical equation : C₆H₁₂O₆ → 2 CH₃CH₂OH + 2 CO₂ The process of culturing yeast under conditions to produce alcohol is referred to as brewing. Yeasts can grow in the presence of up to about 20% alcohol, but the concentration of alcohol in the final product can be increased by distillation. In order to produce ethanol from starchy materials such as cereal grains, the starch must first be broken down into sugars. In brewing beer, this has traditionally been accomplished allowing the grain to germinate, or malt. In the process of germination, the seed produces enzymes that can break its starches into sugars. For fuel ethanol, this hydrolysis of starch into glucose is accomplished more rapidly by treatment with dilute sulfuric acid, fungal amylase enzymes, or some combination of the two. Potentially, glucose for fermentation into ethanol could also be obtained from cellulose. Cellulosic ethanol is a blend of normal ethanol that can be produced from a great diversity of biomass including waste from urban, agricultural, and forestry sources. There are at least two methods of production of cellulosic ethanol - enzymatic hydrolysis and synthesis gas fermentation. Neither process generates toxic emissions when it produces ethanol. The technology is very new and exists in pilot configurations where testing is ongoing. Realization of this enzymatic hydrolysis would turn a number of cellulose-containing agricultural byproducts, such as corncobs, straw, and sawdust, into renewable energy resources. Until recently, the cost of the cellulase enzymes that could hydrolyse cellulose was prohibitive. The Canadian firm Iogen brought the first cellulose-based ethanol plant on-stream in 2004. In April 2004, Iogen became the first business to commercially sell cellulosic ethanol. The primary consumer thus far has been the Canadian government, which, along with the United States government (particularly the Department of Energy's National Renewable Energy Laboratory), has invested millions of dollars into assisting the commercialization of cellulosic ethanol. [http://www.genencor.com/ Genencor] and [http://www.novozymes.com/ Novozymes] are two other companies that have received United States government Department of Energy funding for research into reducing the cost of cellulase, a key enzyme in the production cellulosic ethanol by enzymatic hydrolysis. [http://www.brienergy.com/ BRI Energy, LLC] is a company whose pilot plant in Fayetteville, Arkansas is currently using synthesis gas fermentation to convert a broad variety of urban, agricultural, and forestry waste into ethanol. Fossil fuels and virtually any blend of biomass could also be used as feedstock. After gasification, anaerobic bacteria (Clostridium ljungdahlii) are used to convert the syngas (CO, CO2, and H2) into ethanol. The heat generated by gasification is also used to co-generate excess electricity. According to US Department of Energy studies conducted by the Argonne Laboratories of the University of Chicago, one of the benefits of cellulosic ethanol is that it reduces [greenhouse gas emissions] (GHG) by 85% over reformulated gasoline. By contrast, sugar-fermented ethanol reduces GHG emissions by 18% to 29% over gasoline. At petroleum prices like those that prevailed through much of the 1990s, ethylene hydration was a decidedly more economical process than fermentation for producing purified ethanol. Recent increases in petroleum prices, coupled with perennial uncertainty in agricultural prices, make forecasting the relative production costs of fermented versus petrochemical ethanol difficult at the present time.

Purification

For a mixture of ethanol and water, there is a maximum boiling azeotrope at 96% ethanol and 4% water. For this reason, fractional distillation of ethanol-water mixtures (of less than 96% ethanol) cannot yield ethanol purer than 96%. Therefore, 95% ethanol in water is a fairly common solvent. Several competing approaches may be used to produce absolute ethanol. To break the azeotrope for performing distillation, a small amount of benzene can be added, and the mixture is again fractionally distilled. Benzene forms a tertiary azeotrope with water and ethanol to remove the last of the water, and a binary azeotrope with ethanol removes most of the benzene. The resulting ethanol is water free, for processes that require it. However, several parts per million of benzene remain, so consumption by humans leads to distinctive liver damage. Nowadays benzene as entrainer is replaced by cyclohexane to avoid the health hazards. Alternatively, a molecular sieve can be used to selectively absorb the water from the 96% ethanol solution. Synthetic zeolite in pellet form can be used, as well as corn grits. The zeolite approach is especially of value, for it is possible to recycle the zeolite in a closed system essentially an unlimited number of times, through drying it with a blast of heated CO₂. Absolute ethanol produced this way has no residual benzene, and can be used as fuel, or, when diluted, can even be used to fortify port and sherry in traditional winery operations. Also possible is the method of pressure swing distillation, which is still a topic of current researches. The idea of pressure swing distillation is, to distillate at 2 different pressure, due to the pressure dependence of the azeotropic composition. For example the first distillation step would be proceeded at a pressure at which the azeotropic composition is above 96% for example 97% afterwards a distillation at a pressure with a lower azeotropic composition would follow. By this it is possible to purify ethanol without the use of an entrainer.

Use

zeolite, USA).]]

As a fuel

Main article: alcohol fuel The largest single use of ethanol is as a motor fuel and fuel additive. The largest national fuel ethanol industries exist in Brazil and the United States. The Brazilian ethanol industry is based on sugarcane; as of 2004, Brazil produces 14 billion liters annually, enough to replace about 40% of its gasoline demand. Most new cars sold in Brazil are flexible-fuel vehicles that can run on ethanol, gasoline, or any blend of the two. The United States fuel ethanol industry is based largely on maize. As of 2005, its capacity is 15 billion liters annually, although the Energy Policy Act of 2005 requires U.S. fuel ethanol production to increase to 7.5 billion gallons (28 billion liters) by 2012. In the United States, ethanol is most commonly blended with gasoline as a 10% ethanol blend nicknamed "gasohol". This blend is widely sold throughout the U.S. Midwest, and in cities required by the 1990 Clean Air Act to oxygenate their gasoline during the winter. Many states mandate that an oxygenate be blended into all gasoline sold in the state to reduce CO2 emissions. MTBE used to be the most common oxygenate but because of groundwater contamination problems it has been replaced with ethanol. In California, for instance, 5.6% of its gasoline blend is ethanol.

Chemicals derived from ethanol

; Ethyl esters In the presence of an acid catalyst (typically sulfuric acid) ethanol reacts with carboxylic acids to produce ethyl esters: : CH₃CH₂OH + RCOOH → RCOOCH₂CH₃ + H₂O The two largest-volume ethyl esters are ethyl acrylate (from ethanol and acrylic acid) and ethyl acetate (from ethanol and acetic acid). Ethyl acrylate is a monomer used to prepare acrylate polymers for use in coatings and adhesives. Ethyl acetate is a common solvent used in paints, coatings, and in the pharmaceutical industry; its most familiar application in the household is as a solvent for nail polish. A variety of other ethyl esters are used in much smaller volumes as artificial fruit flavorings. ; Vinegar Vinegar is a dilute solution of acetic acid prepared by the action of Acetobacter bacteria on ethanol solutions. Although traditionally prepared from alcoholic beverages including wine, apple cider, and unhopped beer, vinegar can also be made from solutions of industrial ethanol. Vinegar made from distilled ethanol is called "distilled vinegar," and is commonly used in food pickling and as a condiment. ; Ethylamines When heated to 150–220 °C over a silica- or alumina-supported nickel catalyst, ethanol and ammonia react to produce ethylamine. Further reaction leads to diethylamine and triethylamine: : CH₃CH₂OH + NH₃ → CH₃CH₂NH₂ + H₂O : CH₃CH₂OH + CH₃CH₂NH₂ → (CH₃CH₂)₂NH + H₂O : CH₃CH₂OH + (CH₃CH₂)₂NH → (CH₃CH₂)₃N + H₂O The ethylamines find use in the synthesis of pharmaceuticals, agricultural chemicals, and surfactants. ; Other chemicals Ethanol is a versatile chemical feedstock, and in the past has been used commercially to synthesize dozens of other high-volume chemical commodities. At the present, it has been supplanted in many applications by less costly petrochemical feedstocks. However, in markets with abundant agricultural products, but a less developed petrochemical infrastructure, such as China, India, and Brazil, ethanol can be used to produce chemicals that would be produced from petroleum in the West, including ethylene and butadiene.

Other uses

Ethanol is also used in antifreeze products for its low freezing point. It is easily soluble in water in all proportions with a slight overall decrease in volume when the two are mixed. Absolute ethanol and 95% ethanol are themselves good solvents, somewhat less polar than water and used in perfumes, paints and tinctures. Other proportions of ethanol with water or other solvents can also be used as a solvent. Alcoholic drinks have a large variety of tastes because various flavor compounds are dissolved during brewing. When ethanol is produced as a mixing beverage it is a neutral grain spirit. A solution of 70% of ethanol is commonly used as a disinfectant. Ethanol is also used in most common antibacterial hand sanitizer gels at a concentration of about 62%. Oddly enough, the peak of the disinfecting power occurs around 70% ethanol; stronger and weaker solutions of ethanol have a lessened ability to disinfect. Ethanol kills organisms by denaturing their proteins and dissolving their lipids and is effective against most bacteria and fungi, and many viruses, but is ineffective against bacterial spores. Wine with less than 16% ethanol cannot protect itself against bacteria. Because of this, port is often fortified with ethanol to at least 18% ethanol by volume to halt fermentation for retaining sweetness and in preparation for aging, at which point it becomes possible to prevent the invasion of bacteria into the port, and to store the port for long periods of time in wooden containers that can 'breathe', thereby permitting the port to age safely without spoiling. Because of ethanol's disinfectant property, alcoholic beverages of 18% ethanol or more by volume can be safely stored for a very long time. The hydroxyl group on the ethanol molecule is an extremely weak acid, but upon treatment alkali metal or a very strong base, an H⁺ can be removed to form an ethoxide ion, C₂H₅O^-.

Hazards

- Ethanol and mixtures with water greater than about 50% ethanol are flammable and easily ignited, although there are some solvents and organic compounds which are even more flammable.
- Ethanol within the human body is converted into acetaldehyde by alcohol dehydrogenase and then into acetic acid by acetaldehyde dehydrogenase. The product of the first step of this breakdown, acetaldehyde, is more toxic than ethanol. Acetaldehyde is linked to most of the clinical effects of alcohol. It has been shown to increase the risk of contracting cirrhosis of the liver, multiple forms of cancer, and alcoholism. The characteristic flushing reaction in some Asians is due to the accumulation of acetaldehyde in individuals who have a relative deficiency of acetaldehyde dehydrogenase.
- Although ethanol is not highly toxic, death from ethyl alcohol consumption is possible when blood alcohol level reaches 0.4%. A blood level of 0.5% or more is commonly fatal. Levels of even less than 0.1% can cause intoxication, with unconsciousness often occurring at 0.3-0.4%. There are often drunk driving laws governing the acceptable levels in the blood while driving or operating heavy machinery, usual limits being 0.05% or 0.08%. Methyl alcohol or methanol, on the other hand, is very toxic, regardless of whether it is unintentionally consumed, absorbed through the skin, or inhaled.
- Ethanol has been shown to increase the growth of Acinetobacter baumannii, the bacteria responsible for pneumonia, meningitis and urinary tract infections. This finding may contradict the common misconception that drinking alcohol can kill off a budding infection. (Smith and Snyder, 2005)

References

- "Alcohol." (1911). In Hugh Chisholm (Ed.) Encyclopædia Britannica, 11th ed. [http://91.1911encyclopedia.org/A/AL/ALCOHOL.htm Online reprint]
- Al-Hassan, A.Y. [http://www.gabarin.com/ayh/Notes/Notes%207.htm "Alcohol and the Distillation of Wine in Arabic Sources."] Accessed 14 November 2005.
- Couper, A.S. (1858). "On a new chemical theory." Philosophical magazine 16, 104–116. [http://web.lemoyne.edu/~giunta/couper/couper.html Online reprint]
- Hennell, H. (1828). "On the mutual action of sulphuric acid and alcohol, and on the nature of the process by which ether is formed." Philosophical Transactions 118, 365–371.
- Lodgsdon, J.E. (1994). "Ethanol." In J.I. Kroschwitz (Ed.) Encyclopedia of Chemical Technology, 4th ed. vol. 9, pp. 812–860. New York: John Wiley & Sons.
- Ritter, S.K. (May 31, 2004). "Biomass or Bust." Chemical & Engineering News 82(22), 31–34.
- Roach, J. (July 18, 2005) [http://news.nationalgeographic.com/news/2005/07/0718_050718_ancientbeer.html "9,000-Year-Old Beer Re-Created From Chinese Recipe."] National Geographic News. Accessed 14 November 2005.
- Smith, M.G., and M. Snyder. (2005). "Ethanol-induced virulence of Acinetobacter baumannii". American Society for Microbiology meeting. June 5-9. Atlanta.

External links

- [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc00/icsc0044.htm International Chemical Safety Card 0044]
- [http://www.cdc.gov/niosh/npg/npgd0262.html NIOSH Pocket Guide to Chemical Hazards]
-
- [http://www.compchemwiki.org/index.php?title=Ethanol Coordinates of the ethanol molecule] on Computational Chemistry Wiki. Accessed on 8 September 2005.
- Ethanol as a Source of Renewable Energy
- [http://www.rengen.info/?p=17 Essay]
- [http://issct.intnet.mu/cpabs.htm Abstracts]
- [http://business.guardian.co.uk/story/0,16781,1648504,00.html Sugar powers a Revolution on Brazil's roads] Category:Over-the-counter substances Category:Alcohol Category:Alcohols Category:Teratogens Category:Solvents Category:Household chemicals ms:Etanol ja:エタノール

Dextrorotation

Dextrorotation is the property of rotating plane polarized light clockwise. Laevorotation is the opposite of dextrorotation. Compounds with these properties are said to have optical activity and consist of chiral molecules. The prefixes D- or (+)- and L- or (-)- are applied in the naming of a compound. D-glucose is dextrorotatory. Category:Stereochemistry Category:Polarization

1958

1958 (MCMLVIII) was a common year starting on Wednesday of the Gregorian calendar.

Events

January

- January 1 - Treaty of Rome founding the EU is implemented
- January 4 - Sputnik 1 falls to Earth from its orbit (launched on October 4 1957)
- January 8 - 14 year old Bobby Fischer wins the United States Chess Championship
- January 13 - 9235 scientists publish a plea to stop nuclear bomb tests
- January 18 - Armed Lumbee Native Americans chase off an estimated 5,000 Klansmen and supporters at the town of Maxton, North Carolina.
- January 23 - Following a two-day general strike, dictator Marcos Pérez Jiménez was overthrown by a militar-popular uprising.
- January 28 - Charles Starkweather and Caril Ann Fugate begin their murder spree with the killings of her parents and infant sister
- January 29 - Police capture Charles Starkweather in Wyoming
- January 31 - The first successful American satellite, Explorer I, is launched into orbit
- January 31 - James Van Allen discovers the Van Allen radiation belt

February

- February 1 - Egypt and Syria unite to form the United Arab Republic
- February 5 - Gamel Abdel Nasser is nominated to be the first president of the United Arab Republic
- February 6 - Munich air disaster - 21 dead, including 7 players for Manchester United
- February 11 - Marshal Chen Yi succeeds Zhou Enlai as Chinese Minister of Foreign affairs.
- February 11 - Ruth Carol Taylor is 1st African American woman hired as a flight attendant
- February 17 - Pope Pius XII declares Saint Clare the patron saint of television
- February 20 - Test rocket explodes in Cape Canaveral
- February 23 - Cuban rebels kidnap 5-time world driving champion Juan Manuel Fangio. They release him 28 hours later
- February 23 - Arturo Frondizi wins presidential elections in Argentina
- February 24 - In Cuba, Radio Rebelde, radio of rebels of Fidel Castro, begins broadcasting from Sierra Maestra
- February 25 - Bertrand Russell launches the Campaign for Nuclear Disarmament
- February 28 - One of the worst school bus accidents in U.S. history occurred at Prestonsburg, Kentucky, killing 27.

March-April

- March 1 - Samuel Alphonsus Stritch, ninth bishop (fourth archbishop) of the Roman Catholic diocese of Chicago, appointed Pro-Perfect of the Propagaion of Faith and thus becomes the first American member of the Roman Curia
- March 2 - A British team led by Sir Vivian Fuchs completes the first crossing of the Antarctic in Snow-cat caterpillar tractors and dogsled teams in 99 days
- March 8 - USS Wisconsin is decomissioned, leaving the United States Navy without an active battleship for the first time since 1896.
- March 11 - The US B-47 bomber drops a nuclear bomb in the Mars Bluff, South Carolina
- March 17 - The United States launches the Vanguard 1 satellite
- March 26 - The United States Army launches Explorer III
- March 27 - Nikita Khrushchev becomes Premier of the Soviet Union
- April 3 - Castro's revolutionary army begins its attacks on Havana
- April 4-April 7 - The first protest march for the Campaign for Nuclear Disarmament from Hyde Park, London to Aldermarston, Berkshire. Demonstrators demand ban of nuclear weapons
- April 4 - The daughter of the actress Lana Turner stabs her mother's gangster lover to death (eventually ruled self defence)
- April 6 - Soraya Esfandiary Bakhtiari divorces the Shah of Iran, Mohammad Reza Pahlavi after she is unable to produce any children.
- April 17 - King Baudouin of Belgium officially opens the World Fair in Brussels, also known as Expo '58.

May-June

- May 1 - Arturo Frondizi becomes President of Argentina
- May 2 - A State of Emergency is declared in Aden
- May 12 - A formal North American Aerospace Defense Command agreement is signed between the United States and Canada
- May 13 - During a visit to Caracas, Venezuela, Vice President Richard M. Nixon's car is attacked by anti-American demonstrators
- May 15 - The Soviet Union launches Sputnik 3
- May 16 - Short-lived outburst of friendship between Arabs and Europeans in Algiers
- May 18 - An F-104 Starfighter sets a world speed record of 1,404.19 mph
- May 20 - Batista's government launches counteroffensive against Castro's rebels
- May 21 - United Kingdom Postmaster General Ernest Marples announces that from December, Subscriber Trunk Dialling will be introduced in the Bristol area. [http://news.bbc.co.uk/onthisday/hi/dates/stories/may/21/newsid_2510000/2510289.stm]
- May 23 - Explorer I ceased transmission
- May 30 - The bodies of unidentified soldiers killed in action during World War II and the Korean War are buried at the Tomb of the Unknowns in Arlington National Cemetery.
- June 1 - Charles De Gaulle is brought out of retirement to lead France by decree for six months
- June 1 - Iceland extends its fishing limits to 12 miles
- June 4 - Charles De Gaulle visits Algeria
- June 16 - Imre Nagy is hanged for treason in Hungary
- June 27 - Peronist party becomes legal again in Argentina
- June 29 - Brazil beat Sweden 5-2 to win the 1958 World Cup

July-August

- July 5 - First ascent of Gasherbrum I, 11th highest mountain in the world
- July 7 - President Dwight D. Eisenhower signs the Alaska Statehood Act into United States law
- July 8 - 7.5 Richter scale earthquake in Lituya Bay, Alaska, causes a landslide that produces a huge 520 meter high wave
- July 10 - First parking meters installed in Britain
- July 14 - Iraqi Revolution: In Iraq the monarchy is overthrown by Arab nationalists and Abdul Karim Qassim becomes the nation's new leader
- July 14 - A left wing military coup in Iraq leads to the murder of the king,

Dextromethorphan

Indications

Pharmacodynamics

Clinical pharmacology

History

See also

Antitussive

Cough suppressants

Expectorants

Cough drops

Controversy

Colloquial term usage

References

Drug

Common cold

Pathology

"Cold" as misnomer

Symptoms

Complications

Prevention

Treatment

Societal impact

History

See also

Note

External links

Further reading

Cough syrup

Cough suppressants

Expectorants

Cough drops

Controversy

Colloquial term usage

References

Salt

Appearance

Consistency

Color

Taste

Odor

Nomenclature

Formation

References

See also

Isomer

History

Different forms of isomerism

See also

Analgesic

Stepwise use

The major classes

Paracetamol and NSAIDs

Opiates and morphinomimetics

Specific agents

Specific forms and uses

Combinations

Topical or systemic

Psychotropic agents

Addiction

See also

Reference

Ethanol

History

Production

Ethylene hydration

Fermentation

Purification

Use

As a fuel

Chemicals derived from ethanol

Other uses

Hazards

See also

References

External links

Dextrorotation

1958

Events

January

February