The Painstaking Biography of a Wonder Drug : THE ASPIRIN WARS: Money, Medicine, and 100 Years of Rampant Competition, <i> by Charles C. Mann and Mark L. Plummer,</i> Alfred Knopf, $35; 387 pages

Headache? Take an aspirin. Wait a minute--what was it you just heard? Oh, go ahead, take that aspirin. All things considered, I would.

Aspirin, the quintessential over-the-counter pill, has had remarkable staying power in its 100 years in America’s medicine chest. Under a host of trademarks--some avoiding mention of its active ingredient--aspirin has been hailed for its curative powers, and reviled because the company that held the original patent, Bayer, once had ties with I. G. Farben, a supporter of Adolf Hitler.

Starting with an 1886 accident in Alsace (then part of Germany), science writers Charles Mann and Mark Plummer use “The Aspirin Wars” to reveal behind-the-scenes machinations in both laboratory and boardroom. A sometimes rocky marriage of business and medical history, the narrative is rich in anecdote but encumbered by more detail than this reader could absorb.

The incident in Alsace involved a pharmacist who mistakenly concocted a coal-tar derivative instead of the requested medication for intestinal parasites. The new mixture did nothing for the patient’s tummy, but did lower his fever. (Fever was a major killer in the 19th Century, and even with the side effect of nausea, the accidental mixture seemed promising.)

Then entering the pharmaceutical business, the Bayer company (whose story this book largely follows) set out to transform the Alsatian error into a new painkiller. It came up with acetylsalicylic acid (ASA), a variant of the original compound, which Bayer patented. They took out the trademark Aspirin.

The wonder drug of its time, aspirin won Enrico Caruso’s allegiance, while Franz Kafka found it to be the only cure for his chronic headaches.

With their product a hit in Europe, Bayer began manufacturing aspirin in a factory on the Hudson in 1903 with an American patent and trademark. The company thrived in both hemispheres until Germany’s defeat in World War I. Then, the company split: The German holdings went to Farben, and American Bayer to Sterling Products, which maintained ties with Germany until the late 1930s.

In 1920 Sterling lost its proprietorship of the Aspirin trademark when Judge Learned Hand ruled that the public treated aspirin as a generic name and pharmacists should label all ASAs “aspirin.” When the patent ran out a few years later, a host of competitors hit the market, including an aspirin that fizzed in a glass (Alka-Seltzer), aspirin with caffeine (Anacin) and one with two antacids (Bufferin). With huge budgets, they fought for the dimes and quarters of the fever-ridden.

By the 1950s, aspirin and its look-alikes comfortably dominated the analgesic market. Then, Tylenol--acetaminophen (APAP), which had been synthesized a decade before aspirin and forgotten--was rediscovered. Unlike aspirin, it didn’t upset the stomach and could be sold in liquid form.

Tylenol shattered aspirin’s market position, especially in the wake of studies linking the use of aspirin with Reye’s syndrome, a deadly child-killer. While still coping with Tylenol in the late 1980s, aspirin lost more of its market to ibuprofen, a drug advertised for its anti-inflammatory action.

Meanwhile, back in 1950, Dr. Lawrence I. Craven in Glendale noticed that some of his tonsillectomy patients bled profusely while recuperating. He traced the bleeding to excessive use of Aspergum (chewable aspirin). Craven reasoned that if aspirin reduced blood’s ability to clot, it would cut the chance of clogged arteries that trigger heart attack.

Urging his patients to take an aspirin or two a day, he wrote up his study of 8,000 patients in the Annals of Western Medicine. His results were ignored because he couldn’t explain why aspirin helped prevent heart attack and stroke.

The authors remind us that aspirin is a paradoxical drug: It reduces fever in sick people, but has no effect on individuals with normal temperature. Likewise, aspirin relieves pain but is not an anesthetic, soothes inflamed joints but leaves normal joints untouched.

Studies of the body’s autoimmune system in the 1970s revealed the existence of prostaglandins, substances produced by arachidonic acid, a fatty acid in the walls of cells. As a player in the autoimmune system, aspirin prevents the synthesis of prostaglandins, which are not stockpiled like hormones but are produced in response to specific stimuli.

Aspirin is a wonder drug again. It has been successful in treating conditions as varied as preeclampsia, which kills fetuses late in gestation, heart disease, senile dementia and osteoporosis.

“The Aspirin Wars” has the answers to questions I never thought to ask, like how pharmaceutical giants and organized medicine negotiate with the Food and Drug Administration. Business needs, it seems, are as crucial as laboratory research in determining what ends up on the drugstore counter. Whatever the formula, I suspect I will never innocently swallow another analgesic again.

Next: Jonathan Kirsch reviews “A History of Private Life, Volume 5” edited by Philippe Aries and Georges Duby (Harvard).