Acetylsalicylic acid

History

Resources

Acetylsalicylic acid, commonly known as aspirin, is the most popular therapeutic drug in the world. It is an analgesic (pain-killing), antipyretic (fever-reducing), and anti-inflammatory sold without a prescription as tablets, capsules, powders, or suppositories. The drug reduces pain and fever, is believed to decrease the risk of heart attacks and strokes, and may deter colon cancer and help prevent premature birth. However, aspirin can have serious side effects, and its use results in more accidental poisoning deaths in children under five years of age than any other drug.

History

In the mid- to late-1700s, English clergyman Edward Stone chewed on a piece of willow bark and discovered its analgesic property after hearing a story that declared a brew from the bark was “good for pain and whatever else ails you.” The bark’s active ingredient was isolated in 1827 and named salicin for the Greek word salix, meaning willow. Salicylic acid, first produced from salicin in 1838 and synthetically from phenol in 1860, was effective in treating rheumatic fever and gout but caused severe nausea and intestinal discomfort.

Acetylsalicylic acid was first synthesized in 1898 by a chemist working at Bayer Laboratories in Germany. Soon thereafter, the process for making large quantities of acetylsalicylic acid was patented, and aspirin—named for its ingredients acetyl and spiralic (salicylic) acid—became available by prescription. Its popularity was immediate and worldwide. Huge demand in the United States brought the manufacture of aspirin to that country in 1915 when it also became available without a prescription.

Acetylsalicylic acid has a number of actions. One of these is as an analgesic. Acetylsalicylic acid blocks the production of hormones (chemical substances formed by the body) called prostaglandins that may be released by an injured cell, triggering release of two other hormones that sensitize nerves to pain. The blocking action prevents this response and is believed to work in a similar way to prevent tissue inflammation. Acetylsalicylic acid is only effective on cells producing prostaglandins—for instance, injured cells. The recommended maximum therapeutic dosages for children (2,000 mg daily, spread over four-500 mg doses separated by at least four hours) and adults of (4,000 mg daily) works best against “tolerable” pain; extreme pain is virtually unaffected, as is pain in internal organs. Its effect lasts for about four hours.

Antipyretic action

Acetylsalicylic acid also reduces fever (antipyresis). This action is believed to occur at the anterior (frontal) hypothalamus, a portion of the brain that regulates such functions as heart rate and body temperature. The body naturally reduces its heat through perspiration and the dilation (expansion) of blood vessels. Prostaglandins released in the hypothalamus inhibit the body’s natural heat-reducing mechanism. As acetylsalicylic acid blocks these prostaglandins, the hypothalamus is free to regulate body temperature. Acetylsalicylic acid lowers abnormally high body temperatures while normal body temperature remains unaffected.

Finally, acetylsalicylic acid reduces the formation of blood clots due to platelet aggregation. It accomplishes this by inhibiting the production of a prostaglandin called thromboxane A₂, which is instrumental in platelet aggregation. This “thinning the blood” can reduce the risk of heart attack and stroke, and so acetylsalicyclic acid is frequently prescribed in low doses (such as 75–80 mg daily) over long periods for at-risk patients.

Despite these benefits, use of acetylsalicylic acid formulations such as aspirin has risks. Aspirin’s availability and presence in many prescription and non-prescription medications makes the risk of accidental overdose relatively high. Children and the elderly are

KEY TERMS

Analgesic —A compound that relieves pain without loss of consciousness.

Antipyretic —Anything that reduces fever.

Hypothalamus —A small area near the base of the brain where release of hormones influence such involuntary bodily functions as temperature, sexual behavior, sweating, heart rate, and moods.

Placenta —An organ that develops in the uterus during pregnancy to which the fetus is connected by the umbilical cord and through which the fetus receives nourishment and eliminates waste.

Platelets —Irregularly shaped disks found in the blood of mammals that aid in clotting the blood.

Prostaglandins —Groups of hormones and active substances produced by body tissues that regulate important bodily functions, such as blood pressure.

Suppository —Medication placed in a body cavity, usually the vagina or rectum, that melts and is absorbed by the body.

particularly susceptible, as their toxicity thresholds are much lower than adults. About 10% of all accidental or suicidal episodes reported by hospitals are related to aspirin.

As aspirin slows down platelet aggregation, its use increases risk of bleeding, a particular concern during surgery and childbirth. Aspirin’s irritant effect on the stomach lining may cause internal bleeding, sometimes resulting in anemia.

Reye syndrome is an extremely rare disease, primarily striking children between the ages of three and 15 years after they have been treated with aspirin for a viral infection. Reye syndrome manifests as severe vomiting, seizures, disorientation, and sometimes coma, which can result in permanent brain damage or death. The cause of Reye syndrome is unknown, but the onset strongly correlates to the treatment of viral infections with aspirin. Incidents of Reye syndrome in children on aspirin therapy for chronic arthritis are significant. In 1985, these observations were widely publicized and warning labels placed on all aspirin medications, resulting in a decline in the number of children with viruses being treated with aspirin and a corresponding decline in cases of Reye syndrome.

Aspirin can adversely affect breathing in people with sinusitis or asthma, and long-term use may cause kidney cancer or liver disease. There is some evidence that it delays the onset of labor in full-term pregnancies and, as it crosses the placenta, may be harmful to the fetus.

See also Analgesia; Anti-inflammatory agents; Anticoagulants.

Resources

BOOKS

Jeffreys, Diarmiud. Aspirin: The Remarkable Story of a Wonder Drug. New York: Bloomsbury, 2004.

O’Neil, Maryadele J. Merck Index: An Encyclopedia of Chemicals, Drugs, & Biologicals, 13th ed. Whitehouse Station, NJ: Merck & Co., 2001.

Rainsford, Kim D., ed. Aspirin and Related Drugs. Boca Raton: CRC, 2004.

PERIODICALS

Kiefer, D. M. “Chemistry Chronicles: Miracle Medicines.” Today’s Chemist 10, no. 6 (June 2001): 59–60.

Acetylsalicylic acid

Acetylsalicylic (pronounced uh-SEE-tuhl-sa-luh-si-lik) acid, commonly known as aspirin, is the most popular therapeutic drug in the world. Sold without a prescription as tablets, capsules, powders, or suppositories (a meltable form for insertion into a body cavity), it reduces pain, fever, and swelling, is believed to decrease the risk of heart attacks and strokes, and may protect against colon cancer and help prevent premature birth. Aspirin is often called the wonder drug, but it can have some serious side effects: its use results in more accidental poisoning deaths in children under five years of age than any other drug.

History

In the mid- to late 1700s, English clergyman Edward Stone chewed on a piece of willow bark and discovered its analgesic (pain-killing) property after hearing an "old wives' tale" that declared a brew from the bark was "good for pain and whatever else ails you." The bark's active ingredient was isolated in 1827 and named salicin from the Greek word salix, meaning "willow." Salicylic acid was first produced from salicin in 1838. It was first produced synthetically (meaning produced in a lab from chemicals) from phenol (an acidic compound) in 1860. This synthetic product was effective in treating rheumatic fever and gout but caused burning of the throat and stomach upset. In 1897, a chemist named Felix Hoffmann, working at Bayer Laboratories in Germany, synthesized acetylsalicylic acid in a successful attempt to eliminate the side effects of salicylic acid.

Soon the process for making large quantities of acetylsalicylic acid was patented (allowing only the person or company who developed the product to manufacture or sell the product for a set number of years). Aspirin—named for its ingredients, acetyl and spiralic (salicylic) acid—became available by prescription. Its popularity was immediate and worldwide. Huge demand in the United States brought manufacture of aspirin to that country in 1915, when it also became available without a prescription.

How it works

Analgesic/anti-inflammatory action. Aspirin is commonly used to relieve pain and reduce inflammation, the body's local response to any event causing tissue damage, which includes pain, redness, swelling, and hotness of the affected area. It works best against pain that is bearable; extreme pain is almost entirely unaffected, as is pain in internal organs. Aspirin blocks the production of hormones (chemical messengers formed by the body) called prostaglandins, which are often released by an injured cell. Prostaglandins in turn trigger the release of two other hormones that make nerves sensitive to pain. Aspirin's blocking action prevents this response and therefore is believed to prevent tissue inflammation. Remarkably, aspirin only acts on cells producing prostaglandins (for instance, injured cells). The effect of each dose lasts approximately four hours.

Words to Know

Analgesic: Compound that relieves pain without inducing loss of consciousness.

Antipyretic: Anything that reduces fever.

Hypothalamus: A small area near the base of the brain where release of hormones influence such involuntary bodily functions as temperature, sexual behavior, sweating, heart rate, and moods.

Platelets: Irregularly shaped disks found in the blood of mammals that aid in clotting the blood.

Inflammation: The body's response to tissue damage, which includes pain, redness, swelling, and hotness of the affected area.

Prostaglandins: Groups of hormones and active substances produced by body tissue that regulate important bodily functions, such as blood pressure.

Antipyretic action. Aspirin's antipyretic (fever-reducing) action is believed to occur at the anterior (frontal) hypothalamus, a portion of the brain that regulates such functions as heart rate and body temperature. The body naturally reduces its heat through perspiration and the dilation (expansion) of blood vessels. Prostaglandins released in the hypothalamus inhibit the body's natural heat-reducing mechanism. As aspirin blocks these prostaglandins, the hypothalamus is freed up to regulate body temperature.

Blood-thinning action. One prostaglandin, thromboxane A₂, aids platelet accumulation. (Platelets are cells involved in the clotting of blood.) Aspirin inhibits thromboxane production, thus "thinning" the blood. It is frequently prescribed in low doses over long periods for at-risk patients to help prevent blood clots that can result in heart attacks and strokes.

Adverse effects

Poisoning. Because aspirin is easily available and is present in many prescription and nonprescription medications, the risk of accidental overdose is relatively high. Children and the elderly are particularly susceptible, as their toxicity thresholds (the point at which the body reacts to a drug dosage as poison) are much lower than average adults. About 10 percent of all accidental or suicidal poisoning episodes reported by hospitals are related to aspirin.

Bleeding. As aspirin slows down platelet accumulation, its use increases risk of bleeding, a particular concern during surgery and childbirth. Aspirin's irritant effect on the stomach lining may cause internal bleeding, sometimes resulting in anemia (a condition in which blood does not have enough red blood cells or hemoglobin to carry a normal amount of oxygen).

Reye's syndrome. Reye's syndrome is an extremely rare disease, usually striking children and teenagers between the ages of three and fifteen who are recovering from a viral infection, such as influenza or chicken pox. Reye's syndrome is characterized by severe vomiting, seizures, and confusion as well as swelling of the brain and the collection of fatty deposits in the liver. If left untreated, the disease can result in coma, permanent brain damage, or death. The cause of Reye's is unknown, but the onset is strongly associated with the treatment of viral infections with aspirin. Incidents of Reye's in children on aspirin therapy for chronic arthritis is significant. In 1985, these observations were widely publicized, and warning labels were placed on all aspirin medications. This resulted in a decline in the number of children with viruses being treated with aspirin and a corresponding decline in cases of Reye's.

Other adverse effects. Aspirin can adversely affect breathing in people with nasal polyps or asthma, and its long-term use may cause kidney cancer or liver disease. There is some evidence that aspirin can delay the onset of labor in full-term pregnancies and, because it crosses the placenta (the organ that provides nourishment to the fetus), may be harmful to the fetus.

Acetylsalicylic acid

Acetylsalicylic acid, commonly known as aspirin, is the most popular therapeutic drug in the world. It is an analgesic (pain-killing), antipyretic (fever-reducing), and anti-inflammatory sold without a prescription as tablets, capsules, powders, or suppositories. The drug reduces pain and fever, is believed to decrease the risk of heart attacks and strokes, and may deter colon cancer and help prevent premature birth . Often called the wonder drug, aspirin can have serious side effects, and its use results in more accidental poisoning deaths in children under five years of age than any other drug.

History

In the mid- to late-1700s, English clergyman Edward Stone chewed on a piece of willow bark and discovered its analgesic property after hearing a story that declared a brew from the bark was "good for pain and whatever else ails you." The bark's active ingredient was isolated in 1827 and named salicin for the Greek word salix, meaning willow. Salicylic acid, first produced from salicin in 1838 and synthetically from phenol in 1860, was effective in treating rheumatic fever and gout but caused severe nausea and intestinal discomfort. In 1898, a chemist named Hoffmann, working at Bayer Laboratories in Germany and whose father suffered from severe rheumatoid arthritis , synthesized acetylsalicylic acid in a successful attempt to eliminate the side effects of salicylic acid, which, until then, was the only drug that eased his father's pain. Soon the process for making large quantities of acetylsalicylic acid was patented, and aspirin—named for its ingredients acetyl and spiralic (salicylic) acid—became available by prescription. Its popularity was immediate and worldwide. Huge demand in the United States brought manufacture of aspirin to that country in 1915 when it also became available without a prescription.

Mechanism of action

Analgesic/anti-inflammatory action

Aspirin's recommended therapeutic adult dosage ranges from 600-1,000 mg and works best against "tolerable" pain; extreme pain is virtually unaffected, as is pain in internal organs. Aspirin inhibits (blocks) production of hormones (chemical substances formed by the body) called prostaglandins that may be released by an injured cell , triggering release of two other hormones that sensitize nerves to pain. The blocking action prevents this response and is believed to work in a similar way to prevent tissue inflammation . Remarkably, aspirin only acts on cells producing prostaglandins—for instance, injured cells. Its effect lasts approximately four hours.

Antipyretic action

This action is believed to occur at the anterior (frontal) hypothalamus, a portion of the brain that regulates such functions as heart rate and body temperature . The body naturally reduces its heat through perspiration and the dilation (expansion) of blood vessels. Prostaglandins released in the hypothalamus inhibit the body's natural heat-reducing mechanism. As aspirin blocks these prostaglandins, the hypothalamus is free to regulate body temperature. Aspirin lowers abnormally high body temperatures while normal body temperature remains unaffected.

Blood-thinning action

One prostaglandin, thromboxane A2, aids platelet aggregation (accumulation of blood cells). Because aspirin inhibits thromboxane production, thus "thinning the blood," it is frequently prescribed in low doses over long periods for at-risk patients to help prevent heart attacks and strokes.

Adverse affects

Poisoning

Aspirin's availability and presence in many prescription and non-prescription medications makes the risk of accidental overdose relatively high. Children and the elderly are particularly susceptible, as their toxicity thresholds are much lower than adults. About 10% of all accidental or suicidal episodes reported by hospitals are related to aspirin.

Bleeding

As aspirin slows down platelet accumulation, its use increases risk of bleeding, a particular concern during surgery and childbirth. Aspirin's irritant effect on the stomach lining may cause internal bleeding, sometimes resulting in anemia .

Reye syndrome

Reye syndrome is an extremely rare disease , primarily striking children between the ages of three and 15 years after they have been treated with aspirin for a viral infection . Reye syndrome manifests as severe vomiting, seizures, disorientation, and sometimes coma , which can result in permanent brain damage or death. The cause of Reye is unknown, but the onset strongly correlates to the treatment of viral infections with aspirin, and incidents of Reye in children on aspirin therapy for chronic arthritis is significant. In 1985, these observations were widely publicized and warning labels placed on all aspirin medications, resulting in a decline in the number of children with viruses being treated with aspirin and a corresponding decline in cases of Reye's syndrome.

Other adverse affects

Aspirin can adversely affect breathing in people with sinusitis or asthma , and long-term use may cause kidney cancer or liver disease. There is some evidence that it delays the onset of labor in full-term pregnancies and, as it crosses the placenta, may be harmful to the fetus.

See also Analgesia; Anti-inflammatory agents; Anticoagulants

Resources

books

Feinman, Susan E., ed. Beneficial and Toxic Effects of Aspirin. Boca Raton, FL: CRC Press, LLC, 1994.

O'Neil, Maryadele J. Merck Index: An Encyclopedia of Chemicals, Drugs, & Biologicals. 13th ed. Whitehouse Station, NJ: Merck & Co., 2001.

Ray, Oakley and Charles Ksir. Drugs, Society & Human Behavior. 8th ed. New York: McGraw-Hill Co., 1998.

periodicals

"Aspirin's Next Conquest: Does it Prevent Colon Cancer?" Journal of the National Cancer Institute (February 2, 1994): 166-68.

Kiefer, D.M. "Chemistry Chronicles: Miracle Medicines." Today's Chemist 10, no. 6 (June 2001): 59-60.

Marie L. Thompson

KEY TERMS

Analgesic

—A compound that relieves pain without loss of consciousness.

Antipyretic

—Anything that reduces fever.

Hypothalamus

—A small area near the base of the brain where release of hormones influence such involuntary bodily functions as temperature, sexual behavior, sweating, heart rate, and moods.

Placenta

—An organ that develops in the uterus during pregnancy to which the fetus is connected by the umbilical cord and through which the fetus receives nourishment and eliminates waste.

Platelets

—Irregularly shaped disks found in the blood of mammals that aid in clotting the blood.

Prostaglandins

—Groups of hormones and active substances produced by body tissue that regulate important bodily functions, such as blood pressure.

Suppository

—Medication placed in a body cavity, usually the vagina or rectum, that melts and is absorbed by the body.

Acetylsalicylic Acid

OVERVIEW

Acetylsalicylic acid (uh-SEE-till-sal-in-SILL-ik As-id, or uh-se-TEEL-sal-ih-SEEL-ik AS-id), more commonly known as aspirin, is the world's most commonly used therapeutic drug. By one estimate, about 137 million aspirin tablets are taken every day throughout the world. The drug is also known by other names including: o-acetoxybenzoic acid; 2-(acetyloxy)-benzoic acid; 2-carboxyphenyl acetate; and benzoic acid, 2-hydroxyacetate, in addition to about ten other systematic names and many common names.

KEY FACTS

OTHER NAMES:

Aspirin; see Overview for more names

FORMULA:

CH₃COOC₆H₄COOH

ELEMENTS:

Carbon, hydrogen, oxygen

COMPOUND TYPE:

Carboxylic acid (organic)

STATE:

Solid

MOLECULAR WEIGHT:

180.17 g/mol

MELTING POINT:

135°C (275°F; decomposes)

BOILING POINT:

Not applicable

SOLUBILITY:

Soluble in water, alcohol, ether, chloroform

The analgesic properties of willow tree bark, from which salicylic acid comes, have been known for well over 3,500 years. They were first described in Egyptian scrolls dating to about 1550 bce and were later recommended by a number of ancient authorities, including the famous Greek physician Hippocrates (c. 460–370 bce), the Roman encyclopedist Aulus Cornelius Celsus (c. 10 bce-date of death unknown), the Roman philosopher Pliny the Elder (23 ce-ce), and the Greek physician Pedanius Dioscorides (40–90 ce).

In the period from 1828 to 1829, the active ingredient in willow bark was first isolated by three individuals, the German pharmacist Johann Büchner (dates not available), the French chemist Henri Leroux (dates not available), and the the Italian chemist, Raffaele Piria (1815–1865). Büchner gave the name salicin to the bitter-tasting yellow crystals extracted from willow bark after the Latin name for the willow tree, Salix. In 1853, the French chemist Charles Frederick Gerhardt (1816–1857) developed a method for reacting salicylic acid (the active ingredient in salicin) with acetic acid to make the first primitive form of aspirin.

For many years the way aspirin works in the body was not understood. Scientists now know that the compound's helpful effects come from its action on prostaglandins. Prostaglandins are hormone-like substances released by cells that are injured. They cause the body to release other substances that sensitize nerve endings to pain and start the healing process. Aspirin blocks prostaglandin production, thus relieving the sensation of pain and the inflammation that are the body's response to injury. Aspirin reduces fever by acting on the region of the brain that regulates body temperature and heart rate. Prostaglandins block the body's natural system for producing heat so that by blocking the release of prostaglandins, aspirin allows the regulation of body temperature to continue as usual. Aspirin's protection against heart attack and stroke occur because of its effect on one special type of prostaglandin, known as thromboxane A2. Thromboxane A2 promotes the accumulation of cells that takes place when a blood clot forms. By blocking or slowing down the production of thromboxane A2, aspirin prevents the formation of blood clots and, hence, the probability of heart attack and stroke.

Interesting Facts

• The name aspirin comes from a very old name for salicylic acid, spiraeic acid.
• After Hofmann's discovery, Bayer received a registered trademark for the name aspirin, meaning that no other company could use the name for acetylsalicylic acid. When Germany was defeated in World War I (1914–1918), Allied forces seized the Bayer company's property and possessions and made the name available to all drug manufacturers.

HOW IT IS MADE

The modern method for making aspirin was developed in 1897 by the German chemist Felix Hoffman (1868–1946), an employee of the German chemical manufacturer Bayer AG Chemical Works. In this procedure, phenol (C₆H₅OH) is treated with sodium hydroxide and carbon dioxide to make salicylic acid. The salicylic acid is then reacted with acetic acid (CH₃COOH) to make acetylsalicylic acid, or aspirin. The preparation of aspirin by this procedure is quite simple and is often assigned to students in beginning high school and college chemistry classes. Aspirin tablets themselves include only acetylsalicylic acid, to which is added a small amount of water, starch and lubricant that act as a binder to hold the tablet together.

COMMON USES AND POTENTIAL HAZARDS

The exclusive use of aspirin is as a medicine. It has three important properties as a drug. It relieves pain, reduces inflammation, and reduces fever. In addition to its effectiveness in treating these medical symptoms, it is inexpensive and available in a variety of forms, including chewable tablets, extended-release formulations, effervescent tablets, and even in chewing gums. Aspirin is often prescribed in low, daily doses as a preventative measure for individuals at risk for heart attack and stroke.

While aspirin has many medical benefits, it is not without risk for some individuals. Some people are allergic to the compound and can not tolerate even a low dose. Such individuals experience a number of symptoms if they ingest high doses of aspirin, symptoms that include ringing in the ears, nausea, vomiting, dizziness, confusion, hallucinations, coma, seizures, rapid breathing, fever, and, in the most severe cases, death. Aspirin use is not recommended in children under the age of twelve who show symptoms of viral infections because it can lead to an extremely rare but deadly complication known as Reye's syndrome.

Words to Know

ANALGESIC

A substance that relieves pain.

THERAPEUTIC

Having healing properties.

FOR FURTHER INFORMATION

Arnst, Catherine. "A Preemptive Strike against Cancer." Business Week (June 7, 2004): 48.

"Aspirin." Plant-Derived Drugs. http://phytomedical.com/Plant/Aspirin.asp (accessed on September 17, 2005).

Jeffreys, Diarmuid. Aspirin: The Remarkable Story of a Wonder Drug. New York: Bloomsbury, 2004.

"Molecule of the Month: Aspirin." http://www.bris.ac.uk/Depts/Chemistry/MOTM/aspirin/aspirin.htm (accessed on September 17, 2005).

See AlsoAcetaminophen

Acetylsalicylic Acid

Aspirin (acetylsalicylic acid, see Figure 1) was introduced as an analgesic (pain-relieving agent) in the late nineteenth century by chemists at Bayer, a German pharmaceutical company. Acetylsalicylic acid is a prodrug and is transformed in the body to salicylate, the active form of the drug. Salicylates are also anti-inflammatory (i.e., prevent swelling and phenomena related to swelling associated with trauma or allergic response). Salicylates were initially isolated from white willow (Salix alba ) bark, from which the name of the drug is derived. Indeed, ancient Greek physicians, notably Hippocrates and Dioscorides, suggested chewing on willow bark to relieve pain.

Although aspirin is chiefly extolled for its analgesic properties, it has other equally important therapeutic benefits. Aspirin is an antipyretic (feverreducing) agent and is used to reduce elevated body temperature. Since the 1980s aspirin has been prescribed for the prevention of heart attack and stroke. Recent studies suggest that aspirin may guard against colon cancer.

Acetylsalicylic acid is a weak acid (pK_a = 3.5) that can be absorbed across the mucosal lining of the stomach. However, most of the drug is absorbed from the upper regions of the small intestine. Once the drug has entered the bloodstream it is hydrolyzed to acetic acid and salicylic acid (see Figure 2).

The most widely recognized mode of action of the salicylates is the inhibition of the formation of prostaglandins. Prostaglandins are 20-carbon molecules having side chains of varying degrees of saturation and oxidation , synthesized from polyunsaturated fatty acids in the body in response to tissue damage. The localized release of prostaglandins in response to injury or invasion by foreign agents (antigens) results in an increased blood flow to the affected area, and stimulation of the sensory nerve endings that mediate pain. Salicylates inhibit prostaglandin synthesis by binding to prostaglandin cyclooxygenases (the enzymes responsible for transforming fatty acids into prostaglandins), thereby inactivating the enzymes.

Aspirin is one of the most widely used drugs in modern society. It is most frequently used to treat mild to moderate pain or to reduce fever. Because of its anti-inflammatory action, aspirin is prescribed to individuals who suffer from joint inflammation conditions such as rheumatoid arthritis and osteoarthritis. In addition to its antipyretic, anti-inflammatory, and analgesic properties, aspirin is also prescribed to patients at high risk for heart attack

or stroke. Salicylates retard the clotting of blood by inhibiting platelet aggregation. When platelets aggregate, clotting is promoted and blood flow through vessels and valves is impeded. A stroke results when blood flow to regions of the brain is blocked. Aspirin inhibits enzymes in platelet membranes responsible for the formation of platelet aggregation factors, and thus reduces the risk of blood clots. Enzyme inhibition may also be responsible for aspirin's purported anticancer action. Recent findings suggest that regular doses of aspirin reduce the risks of some cancers (particularly colon cancer). Although scientists do not know how aspirin reduces the risk of cancer, they suspect it could be related to its anti-inflammatory effects and its ability to inhibit enzymes produced by some cancer cells.

Not all of aspirin's health effects are beneficial. Salicylate therapy is associated with many adverse side effects, generally pertaining to the gastrointestinal system. Gastric ulcers and gastric bleeding can occur in individuals on high doses of aspirin. More worrisome is the occurrence of Reye's syndrome in children with viral illnesses such as influenza or chicken pox who have been given aspirin. Reye's syndrome is a serious condition characterized by sudden vomiting, violent headaches, and, in 20 to 30 percent of cases, death. Because of the potential risk of Reye's syndrome in young people administered aspirin, many physicians and the Food and Drug Administration (FDA) warn against the use of salicylates in children under sixteen years of age.

FRIEDRICH BAYER (1825–1880)

In 1863 Friedrich Bayer cofounded a dye manufacturing company in Germany. Eight years after his death, in 1888 the company opened a pharmaceutical division. A decade later, employee Felix Hoffman, concerned over his father's aches and pains, discovered a useful chemical in the waste of the dye process. Known as aspirin, it remains a popular painkiller over 100 years later.

—Valerie Borek

see also Acetaminophen; Acid-Base Chemistry; Hydrolysis; Ibuprofen.

Nanette M. Wachter

Bibliography

Chevallier, Andrew (1996). The Encyclopedia of Medicinal Plants. New York: D.K. Publishing.

Kolata, Gina (2003). "Aspirin, and Cousins, Take a New Role in the War on Cancer." New York Times, March 11, 2003. Section F:1.

Williams, David A.; and Lemke, Thomas L. (2002). Foye's Principles of Medicinal Chemistry, 5th edition. Baltimore: Lippincott Williams & Wilkins.