For more than 100 years the safest, most effective, least expensive and widest-ranging drug known to man has been available to ease headaches, stop inflammation and lower fever.

It has been implicated in reducing the risk of heart attack and stroke, cancer of the pancreas, colon and ovaries, and in mediating sunburn. It was the first synthetic drug and is so powerful that if it were introduced today it would probably be by prescription only.

What is this wonder drug? It is ordinary, run-of-the mill aspirin.

Despite the potential for stomach upset and long-term damage to stomach linings, it continues to be the most widely used drug in the world. The aspirin produced every year is enough to make a chain of tablets that would stretch from the Earth to the moon and back. The United States alone consumes roughly 80 billion aspirin tablets annually.

German chemist Felix Hoffmann developed aspirin in modern form in 1897 as a treatment for his father’s arthritis. Nearly 40 years earlier a French chemist had made some but did not see much of a use for it, considered it too tedious to make, and gave up.

Long before that, more than 3,500 years ago, the Sumerians and Egyptians used it, but in a different form. The Ebers papyrus, a collection of medicinal recipes from the middle of the second millennium B.C., prescribed a tea of dried myrtle leaves for muscle, joint and back pain.

In the fifth century B.C., Hippocrates, the father of modern medicine, used ground willow bark to ease aches and pains.

Willow bark and myrtle contain salicylates, a class of chemicals with analgesic properties. The name is derived from the Latin word for willow: salix.

Aspirin (acetylsalicylic acid) and wintergreen oil (methyl salicylate) are the two most familiar salicylates, although salicylic acid is still used in poultices and tinctures to remove corns, callouses and warts.

From early in the 19th century salicylic acid and its chemical relatives were used to treat the pain and swelling of arthritis and to help reduce fevers. The problem with these chemicals was that they were used at high doses and caused upset and bleeding in the stomach and digestive tract. Hoffmann worked so hard to develop a mild form of the drug because his father suffered from arthritis and the negative effects of salicylic acid.

It was not until 1971 that an English physician, Sir John Vane, discovered that aspirin works by inhibiting the body’s production of a hormone-like chemical called prostaglandin, for which he received the 1981 Nobel Prize.

Prostaglandin is one of a series of biochemicals that the body uses to call attention to injury by causing pain. Prostaglandins not only cause pain from damaged tissue, but they also cause the surrounding area to become inflamed, bathing the tissues in fluid that protects it and promotes healing.

Cells in damaged tissues make prostaglandin using an enzyme called cyclooxygenase 2, or COX-2. Aspirin does not stop the problem that is causing the pain, but it does lower the volume on the pain signals to the brain by blocking the COX-2 enzymes. An enzyme is like a key that must be inserted to unlock a lock, and aspirin works by blocking the keyhole and preventing the COX-2 key from being inserted.

Aspirin also blocks the production of another prostaglandin (thromboxane) that causes platelets to clump together to form a blood clot. This can be a good thing if it stops clots from forming in the arteries and capillaries of the heart, lungs and brain, but a bad thing if you have a stroke, need surgery or get a cut or a bloody nose.

Richard Brill is a retired professor of science at Honolulu Community College. His column runs on the first and third Fridays of the month. Email questions and comments to brill@hawaii.edu.