These days we have access
to a huge array of medicines to protect us from pain, disease and death.
But, as Michael Mosley has been discovering, the source of many of our
more remarkable medicines have been deadly poisons.
Take a look at this picture.
It is the most poisonous substance known to man. A couple of
teaspoons would be enough to kill everyone in the UK. A couple of kilos
would kill every human on earth. It is so dangerous that it is
manufactured in military installations and at around £100 trillion per
kilo it is also the most expensive substance ever made. Yet despite
being so toxic and so costly it is in huge demand. Many people pay large
amounts of money to have it injected into their foreheads.
It is botulinum toxin - better known as Botox - a toxin
produced by bacteria first discovered in poorly prepared sausages during
the 18th Century. It was named after the Latin for sausage - botulus.
On the LD50 toxicity scale, which measures how
much of a substance you would need to kill half the people it is given
to, Botox measures just 0.000001 mg/kg. In other words you need would
need around 0.00007mg to kill a 70kg man like me. Or to put it another
way, a lethal dose for me would weigh less than one cubic millimetre of
Botulinum toxin kills its victims by causing respiratory
failure. It is a neurotoxin - it enters nerves and destroys vital
proteins. This stops communication between nerves and muscles. Only the
growth of new nerve endings can restore muscle function, and that can
Its main claim to fame is that it will iron out wrinkles in
ageing faces and does so by destroying the nerves that cause frowning.
The quantities used are tiny - a few billionths of a gram, dissolved in
saline. In the name of science I tried Botox a few years ago.
It certainly smoothed away the wrinkles but it also gave me a weird expression, until the new nerve endings grew.
But botulinum toxin is far more than simply a vanity product.
It is extremely useful for treating a number of medical conditions,
ranging from eye squints to migraines, excess sweating to leaky
bladders. In fact there are currently more than 20 different medical
conditions that botulinum toxin is being used to treat. More are being
discovered all the time.
Botulinum toxin is just one example of extraordinarily dangerous
poisons that have useful medical applications. Captopril, a $1bn
antihypertensive drug, was developed from studies made on snake venoms.
Exenatide, marketed as Byetta, is an effective and extremely lucrative
drug used to treat type-2 diabetics. It comes from studies of the saliva
of the Gila monster, a large venomous lizard that lives in the
south-western US and Mexico
But the impact of poisons on modern medicine go deeper than
simply providing new forms of treatment. One poison in particular helped
shape the entire modern pharmaceutical industry.
In Victorian Britain, life insurance was a booming industry. This easy money led to a surge in murders, many of them by poison.
One of the most high profile cases was a woman called Mary Ann Cotton
who, in 1873, was tried for multiple murders. She had been married four
times and three of her husbands, all heavily insured, died. The one who
survived seems to have done so because he refused to take out
insurance. So she left him.
In all, 10 of her children died of what seemed to be
gastric-related illnesses. Each must have been a tragic loss, but
fortunately for Cotton most were insured.
Her mother, her sister-in-law, and her lover all died. And in
each case, she benefited. By 1872, the unfortunate woman had lost an
astonishing 16 close friends or family members. But there was one left -
her seven-year-old stepson, Charles. She tried to give him away to the
local workhouse but they wouldn't have him. So young Charles soon died.
The manager of the workhouse, however, got suspicious and
contacted the police. They soon decided Cotton must have poisoned the
boy and thought they knew how she'd done it - with arsenic.
Arsenic oxides are minerals and as a poison are almost
unrivalled. They are tasteless, dissolve in hot water and take less than
a hundredth of an ounce to kill. Yet in the 19th Century, marketed as a
rat poison, arsenic oxide was cheap and easily available. Children
would blithely collect it from the shops along with the tea, sugar and
The trial of Mary Ann Cotton would hinge on whether they
could find traces of arsenic in the body of her stepson. Forensic
science was still in its infancy but they did have a good test for
arsenic. This was because there was an awful lot of arsenic poisoning
A sample from the boy's stomach and intestines
was heated with acid and copper. If arsenic was present, the copper
would turn dark grey and, when placed on paper soaked in mercury
bromide, produce a tell-tale yellowy-brown stain.
When they tested the body of poor little Charles they
discovered that he had indeed died of a lethal dose of arsenic. Cotton
was convicted of his murder and hanged in Durham Jail. She was never
taken to trial for the mysterious deaths of her mother, three husbands,
two friends and 10 other children.
It was a rash of murders and poisonings like this one that
led first to the Arsenic Act and then to the Pharmacy Act 1868. This act
ruled that the only people who could sell poisons and dangerous drugs
were qualified pharmacists and druggists.
So it was from poisonings, accidents and murders that the
modern legitimate business of pharmacy finally emerged. And one compound
- arsenic trioxide - has also found a legitimate medical use, as an