Yet Heinrich Dreser, chemist and opportunist, was one of the most influential men of his age.

Between 1897 and 1914, Dreser worked for Bayer, the former dye factory that was to become the first of the world's pharmaceutical giants, in Wuppertal, north-west Germany.

Friedrich Engels was born there. While Dreser made less of a mark on history, you could argue he had the greater influence on the 20th century. As head of Bayer's pharmacological laboratory, he was responsible for the launch of two drugs that have shaped the way we live: aspirin, the world's most successful legal drug; and heroin, the most successful illegal one.

Aspirin, of which the world now consumes 40 billion tablets a year, was launched 100 years ago next February. A fanfare of publicity will mark the centenary.

The centenary of heroin is more ambiguous: it was launched in November 1898 but was registered as a trademark in various countries from June that year, most lucratively in the US in August. But whenever the centenary falls, Bayer won't be celebrating.

This is understandable; but the stories of aspirin and heroin are intertwined, not least through Dreser.

Born in 1860, in Darmstadt, the son of a physics professor, he showed promise as a chemist from an early age. After receiving his doctorate from Heidelberg University, he worked in various laboratories before becoming a professor at Bonn University in 1893. Four years later he joined the Bayer Company, where he was in charge of testing the efficacy and safety of new drugs.

Dreser was admired for his thorough, methodical approach, and for his innovations in testing (he was, for example, the first chemist to use animal experiments on an industrial scale). The credit for originating new products for Bayer belonged, strictly speaking, to the researcher Arthur Eichengruen, but Dreser had the power to decide which new products would be developed. He had also negotiated a special deal which guaranteed him a share of the profits from products he launched.

In 1897 the Bayer chemist Felix Hoffmann, acting on Eichengruen's instructions, discovered a new process for modifying salicyclic acid (a remedy for fever and inflammation which unfortunately has excruciating digestive side effects) to produce acetylsalicyclic acid (ASA).

This compound, later to be named Aspirin, had been isolated before and the healing powers of salicylates (derived from willow bark) had been known for centuries. But Hoffmann had created a reliable process for making it.

Eichengruen enthusiastically recommended ASA to Dreser in 1898. Dreser, after cursory consideration, rejected it. Ostensibly, his objection was that ASA would have an "enfeebling" action on the heart. "The product has no value," he pronounced confidently. But the real problem was almost certainly that he had another product on his mind whose impending success he was anxious not to jeopardise. This was heroin.

Like aspirin, the drug that Bayer launched under the trademark Heroin in 1898 was not an original discovery. Diacetylmorphine, a white, odourless, bitter, crystalline powder deriving from morphine, had been invented in 1874 by an English chemist, C R Wright.

But Dreser was the first to see its commercial potential. Scientists had been looking for some time for a non-addictive substitute for morphine, then widely used as a painkiller and in the treatment of respiratory diseases. If diacetylmorphine could be shown to be such a product, Bayer - and Dreser - would hit the jackpot.

Diacetylmorphine was first synthesised in the Bayer laboratory in 1897 - by Hoffmann, two weeks after he first synthesised ASA. The work seems to have been initiated by Dreser, who was by then aware of Wright's discovery, even though he subsequently implied that heroin was an original Bayer invention.

By early 1898 was testing it on sticklebacks, frogs and rabbits. He also tested it on some of Bayer's workers, and on himself. The workers loved it, some saying it made them feel "heroic" (heroisch). This was also the term used by chemists to describe any strong drug (and diacetylmorphine is four times stronger than morphine). Creating a brand name was easy.

In November 1898, Dreser presented the drug to the Congress of German Naturalists and Physicians, claiming it was 10 times more effective as a cough medicine than codeine, but had only a tenth of its toxic effects. It was also more effective than morphine as a painkiller. It was safe. It wasn't habit-forming. In short, it was a wonder drug - the Viagra of its day.

"What we don't recognise now," says David Muso, professor of psychiatry and the history of medicine at Yale Medical School, "is that this met what was then a desperate need - not for a painkiller, but for a cough remedy".

Tuberculosis and pneumonia were then the leading causes of death, and even routine coughs and colds could be severely incapacitating. Heroin, which both depresses respiration and, as a sedative, gives a restorative night's sleep, seemed a godsend.

The initial response to its launch was overwhelmingly positive. Dreser had already written about the drug in medical journals, and studies had endorsed his view that heroin could be effective in treating asthma, bronchitis, phthisis and tuberculosis. Now mailshots and free samples were sent out by the thousand to physicians in Europe and the US. The label on the samples showed a lion and a globe. (There is a notorious brand of Burmese heroin, Double Globe, that uses remarkably similar packaging today.)

By 1899, Bayer was producing about a ton of heroin a year, and exporting the drug to 23 countries. The country where it really took off was the US, where there was already a large population of morphine addicts, a craze for patent medicines, and a relatively lax regulatory framework. Manufacturers of cough syrup were soon lacing their products with Bayer heroin.

There were heroin pastilles, heroin cough lozenges, heroin tablets, water-soluble heroin salts and a heroin elixir in a glycerine solution. Bayer never advertised heroin to the public but the publicity material it sent to physicians was unambiguous. One flyer described the product thus: "Heroin: the Sedative for Coughs . . . order a supply from your jobber."

"It possesses many advantages over morphine," wrote the Boston Medical and Surgical Journal in 1900. "It's not hypnotic, and there's no danger of acquiring a habit."

But worrying rumours were surfacing. As early as 1899, researchers began to report patients developing "tolerance" to the drug, while a German researcher denounced it as "an extremely dangerous poison". By 1902 - when heroin sales were accounting for roughly five percent of Bayer's net profits - French and American researchers were reporting cases of "heroinism" and addiction.

The bandwagon took time to stop. Between 1899 and 1905, at least 180 clinical works on heroin were published around the world, and most were favourable, if cautious. In 1906, the American Medical Association approved heroin for medical use, though with strong reservations about a "habit" that was "readily formed".

But with the accumulation of negative reports and the steady encroachment on the market by other manufacturers, it was clear heroin would never deliver the riches that Dreser had yearned for.

Had heroin been his only pet project, this disappointment could have spelt career disaster. Dreser had the kind of personality that needed commercial results to lend it plausibility. With his unfashionably formal clothes and his habit of dragging an overweight dachshund to work with him, he was seen as an eccentric loner, a "difficult" man whose ready sarcasm and autocratic manner meant he did not want for enemies.

Luckily, although his first "baby" was showing signs of turning into a monster, Dreser had belatedly adopted another: aspirin. Eichengruen, refusing to accept Dreser's rejection of ASA, had continued to investigate it and to lobby for its development. Eventually, Dreser recognised which way the wind was blowing, tested ASA on himself (as well as on his laboratory of rabbits), and finally published an enthusiastic scientific paper recommending it, particularly for the treatment of rheumatism - but omitting to mention the contributions of Eichengruen and Hoffmann. In February 1899, the brand name "Aspirin" was registered, and in June, Dreser presided over its launch.

Like heroin, aspirin more or less sold itself. As a painkiller without undesirable side effects, it was - and remained for decades - unique. By the end of 1899 it was being used all over Europe and the US, and by the time the heroin bubble burst, aspirin had more than filled the gap. Bayer was on its way to becoming an industrial giant. Hoffman and Eichengruen do not seem to have received any special compensation for their efforts. For Dreser, though, the rewards were spectacular.

In 1913, Bayer decided to stop making heroin. There had been an explosion of heroinrelated admissions at New York and Philadelphia hospitals, and in East Coast cities a substantial population of recreational users was reported (some supported their habits by collecting and selling scrap metal, hence the name "junkie"). Prohibition seemed inevitable and, sure enough, the next year the use of heroin without prescription was outlawed in the US. (A court ruling in 1919 also determined it illegal for doctors to prescribe it to addicts.)