It may seem that discoveries in science can be made quite by accident. This is true — there are a lot of drugs that were discovered unplanned. True, on the other hand, they were opened after all by specialists, and not by strangers. As Goethe said, “Discovery requires luck, ingenuity and intellect — and one cannot do without the other.” We tell where the contribution of luck turned out to be the highest: what medicines were discovered by chance.

mold in the cup

A classic example of an accidental discovery is the well-known penicillin. It was discovered, as you know, by Alexander Fleming, who, for a start, did not close the window in the laboratory, having gone on vacation. And upon his return, he found mold in a Petri dish — a flat container for experiments.

Who would have thought that this dirty container and the unclosed window would be given such importance? But even today it is not entirely clear whether Fleming deliberately left the Petri dish with bacteria and opened the window, or, more likely, he really suffered from forgetfulness and could not stand washing test tubes.

Who else — and even a scientist — would calmly throw out such dirt. But Fleming successfully became interested in what is there that has grown on the surface of the culture medium with dangerous Staphylococcus aureus bacteria.

Upon closer examination, it turned out that from the mold spores that were brought with the air, the fungus Penicillium grew, successfully suppressing the growth of bacteria: they did not grow next to its threads.

Thus, the world’s first antibiotic was discovered, although decades passed before its mass production.

New Zealand scientists also relied on intuition and luck when they accidentally discovered a new preventive property of the meningitis vaccine: it turns out that this vaccine also protects against gonorrhea, as reported in an article in The Lancet published in 2019.



Several classes of drugs for depression were also discovered by accident. Inproniazid, for example, was used in the treatment of tuberculosis before its effect on mood was discovered. Tricyclic drugs were first tried to treat schizophrenia. And the first benzodiazepine, like penicillin, was found in a forgotten test tube.

Leo Sternbach tried to develop tranquilizers, but for a long time he did not succeed, and he moved on to work on the creation of dyes. A few months later, while cleaning the laboratory, one of the employees found in the closet a forgotten sample from the first experiments with a “beautiful crystalline” compound. But he did not begin to conduct tests immediately (although he did not throw it away), scientists returned to work on tranquilizers after another couple of years.

As a result, this substance was named chlordiazepoxide, the first benzodiazepine tranquilizer with a strong sedative, muscle relaxant and anticonvulsant effect.

Interestingly, this forgotten test tube was the last untested of more than two hundred samples that Sternbach studied in the first series of experiments that lasted two years.

It is interesting!

And we owe the discovery of the popular blood-thinning drug warfarin not even to a laboratory employee, but to … veterinarians. It was they who noticed that in cattle that graze on clover, the resulting wounds bleed for a long time.

Experts shared this fact with colleagues who no longer used animals, but people. Thus, the first step was taken towards the creation of an anticoagulant, as well as to understanding the role of vitamin K in the prevention of thrombosis.

Lithium preparations

Today, lithium is relevant in the treatment of manic states and some types of psychosis. And in the 19th century, they were actually treated for gout and urolithiasis. And they were treated until the middle of the last century, when psychiatrist John Cade, in an attempt to find out the nature of mental illness, conducted specific experiments: he injected the urine of healthy and sick people into the abdominal cavity of guinea pigs.

It turned out that with injections from sick patients, the mumps lived less, and the psychiatrist came to the conclusion that there was an excess of uric acid in it. To dissolve uric acid, the doctor began to use an additive in the form of a lithium solution. And the pigs after the procedure began to look much calmer than one would expect after an injection in the stomach.

Actually, this is how lithium preparations began to be used in psychiatry. And the doctor first checked their safety for people on himself, and then he began to treat patients.

Did you know?

Injections of botulinum toxin, or Botox, were not first used in salons at all. Botulinum toxin in 1970 was a drug that helped ophthalmologists determine which muscles in monkeys are involved in the movement of the eyeballs. It was injected into the extraocular muscle and checked for paralysis.

And only 20 years later, botulinum toxin entered the beauty industry — and then at first for the treatment of facial asymmetry. Beauty, by the way, its use is not limited today: more about where else this poison is used, read in a separate article.

Blue pills for potency

Blue pills for potency

Sildenafil itself, which is now used in potency pills, was deliberately searched for by scientists. The discovery of this substance cannot be called accidental — only they were going to treat not erectile dysfunction, but angina pectoris: sildenafil actually relaxes blood vessels in the heart area and improves blood circulation. Everything was revealed at the stage of clinical trials.

Male volunteers were quite surprised (and many were pleased) with regular «unprovoked» erections during the period of taking the drug «for the heart.» The manufacturer, of course, did not pass by such a side effect, and after new tests, the blue pills went to conquer the planet.

Did you know?

But Argentine scientists decided to see what would happen if you give sildenafil to hamsters. It is not clear how and why they conducted this study, but it turned out that while taking the drug, hamsters are easier to tolerate jet lag.

Scientists were awarded the Ig Nobel Prize for the most useless discovery in 2007.



It is understandable when doctors, biologists, chemists become the authors of medical discoveries, even if they are accidental. But the first pacemaker that can be implanted was invented by an engineer. Although he did not work on it at all.

American Wilson Greatbatch back in 1958 tried to create an apparatus that would record the rhythm of the heartbeat. But he mixed up the resistors — and instead of recording, his device began to emit rhythmic electrical impulses, repeating the activity of a healthy heart.

Fortunately, the engineer immediately understood the potential significance of the new apparatus. And after two years of work on a new device, a patent was filed for an implantable pacemaker.

Improved «descendants» of this first accidental discovery today save the lives of more than five hundred thousand people every year. True, today with these devices sometimes there are such problems that Greatbatch never dreamed of: read about it in the article “Medical hacking: how to hack a pacemaker?”.

Lithium preparations in psychiatry, narcology and neurology (to the 70th anniversary of John Cade’s discovery). Part I. Historical / Becker R.A., Bykov Yu.V. // Acta Biomedica Scientifica. 2019 #1

The history of tricyclic antidepressants and its implications for modern psychopharmacotherapy / Danilov D.S. // Social and Clinical Psychiatry 2019 #2

Effectiveness of a Group B Outer Membrane Vesicle Meningococcal Vaccine in Preventing Hospitalization from Gonorrhea in New Zealand: A Retrospective Cohort Study / Paynter J, Goodyear-Smith F, Morgan J, et al. // Vaccines (Basel) 2019