There are lots of ways to numb yourself to
the minor aches and pains that we humans accrue
in our daily lives, but today we’re talking
about aspirin.
Why aspirin?
Because although aspirin as we know it has
only existed since the late 1800s, the plant
that it was originally derived from, willow,
is probably the oldest known painkiller in
history.
Records of people using willow leaves to relieve
pain and fevers stretch back 6,000 years to
ancient Assyria and Sumer.
Willow was also put to use in ancient Egypt,
Babylon, and China – and Hippocrates thought
it was pretty rad, especially for pain during
childbirth.
In the 17 and 1800s, scientists worked on
identifying, extracting, and purifying the
active ingredient in willow, which turned
out to be a chemical they called salicin.
Which, they further discovered, your digestive
system changes into salicylic acid.
Which is what reacts with stuff in your body
to relieve pain, reduce fever and swelling,
and etcetera.
More on how all that works in a second.
First: salicylic acid.
German chemists figured out how to synthesize
it on an industrial scale in the 1870s, effectively
ending millennia of willow powder use.
But it had its drawbacks – lots of patients
couldn’t stomach it.
Literally.
It was really hard on the stomach lining.
The son of one such patient, a chemist with
Friedrich Bayer & Co. by the name of Felix
Hoffmann, thought it might be less irritating
if it was less acidic.
So Hoffmann converted it to what Bayer & Co.
dubbed Aspirin in 1899.
Aspirin has become the popular (and less-ridiculous-to-pronounce)
name for Hoffmann’s chemical compound: acetylsalicylic
acid, or salicylate.
It works, as humanity finally figured out
in the 1970s, by preventing your cells from
using cyclooxygenase-2 to create prostaglandins.
And don’t worry, I’m about to unpack that.
Let’s start with the idea that lots of pain
is useful, evolutionarily speaking.
When you feel pain due to an injury, like
a burn or a twisted ankle, it prompts you
to take your hand away from the hot thing
right quick, or to keep your weight off the
ankle until it heals.
Useful.
Pain from an injury to anything-but-the-nervous-system
is called nociceptive pain -- after specialized
sensory neurons located throughout your body
called nociceptors.
They alert your brain to damage with the help
of the damaged tissue itself.
Cells in the hurt area start producing enzymes
that work together to create a few signal
chemicals, including those prostaglandins
I mentioned a minute ago.
Prostaglandins tell your nociceptors: “No,
hey, seriously, there’s a problem here.”
They make your nociceptors increase the signal
to your brain.
You feel the pain more acutely.
Prostaglandins are also one of the chemicals
that cause inflammation in the tissue around
a wound.
They make your blood vessels expand, flooding
the damaged tissue with all the immune-system
stuff your body sends to protect the wound
from infection and to help it heal.
All of this is great right up until it isn’t.
After a certain point, you don’t need continual,
acute pain as a reminder that you’re injured.
And some nociceptive pain and swelling is
warning us about stimuli that we can’t easily
avoid: like headaches, arthritis, or period
cramps.
Here’s where aspirin swoops in to save the
day.
When you take aspirin, it’s absorbed by
your digestive tract into your bloodstream,
which takes it throughout your body – including
places where cells are excreting the enzymes
necessary to produce prostaglandins.
Molecules of aspirin lock up with one of those
enzymes: cyclooxygenase-2.
Once a molecule of cyclooxygenase-2 is locked
into a molecule of aspirin, it can’t help
create prostaglandins.
Which means fewer prostaglandins, which means
that the pain signals to your brain don’t
increase as much and the tissue in the area
doesn’t swell as much.
Thanks, aspirin!
And thousands of years of science!
What other medicines are you curious about?
Let me know in the comments, and maybe my
next headache will be trying to figure that
medicine out.
Give us a like – and subscribe – if you
learned something here.
And for lots more about sources of and remedies
for pain, visit our home planet: HowStuffWorks.com.
