Acetylsalicylic Acid

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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.