You ever see those commercials suggesting people take a tiny dose of aspirin every single
day?
It’s an amount so small it doesn’t really work, at least for pain relief, yet taking
low-dose aspirin is fairly common, among those at risk for heart attacks or stroke.
Here’s why aspirin works in a baby-sized dose.
Remember: The only thing worse than a fake TV doctor is a fake YouTube doctor.
We’re here to tell you how aspirin works, not what you should do with it.
Talk about this stuff with your doctor, not us.
This small 81 mg dose of aspirin is sometimes called “baby aspirin” because it was originally
meant for kids.
But aspirin is rarely given to children any more due to their elevated risk of a serious
brain and liver condition called Reye’s syndrome.
Instead, low dose aspirin has found a new niche: being taken daily by folks at risk
of a heart attack -- or other conditions related to blood clots, like stroke.
Aspirin, or acetylsalicylic acid, is a molecule with an impressive pedigree.
Its close chemical cousin salicylic acid, derived from natural sources like willow bark,
has been in use as a pain reliever for literally thousands of years.
Since 1897, we’ve used aspirin instead, which does the same things, it’s just easier
on the stomach.
The things aren’t limited to relieving pain; they also include reducing inflammation and
preventing blood clots.
Blood clotting is a good thing when you’ve got a big gash in your arm and your blood
is rapidly going from being inside your body to being outside it.
Small bodies called platelets clump together and block off the flow of blood, halting its...rapid
escape.
But when those clumps form inside your veins and arteries, it can be pretty bad news.
When a blood clot interferes with the flow of blood to the heart, it’s a heart attack.
If it’s blocking off a part of your brain, that’s a stroke.
And other parts of the body can be affected as well, by what’s more generally referred
to as a thrombosis.
You really don’t want blood clots anywhere inside you.
Which is why many people, especially if they’ve already had a heart attack or stroke or been
diagnosed with coronary artery disease, may be advised by their doctor to take a low dose
of aspirin every day to prevent blood clots from causing another serious incident.
Here’s how it works.
When a platelet cell detects an injury, it kicks off a series of chemical reactions that
result in the production of thromboxane A2 – a chemical signal that helps recruit other
platelets to form a clump, which is to say, a blood clot.
This process starts with a type of fatty acid called arachidonic acid.
The enzyme COX-1 catalyzes the reaction of this molecule into prostaglandin H2, or PGH2
for short.
PGH2 is crucial for blood clotting because it’s the precursor molecule needed to create
the clotting signal thromboxane A2.
This is where aspirin comes in.
The COX-1 enzyme has a cleft in its structure that’s a perfect fit for arachidonic acid.
The aspirin binds to the enzyme and blocks the arachidonic acid from entering this pocket,
which puts the brakes on the production of PGH2.
No PGH2 means no signals can be made from it, and that makes it much harder for blood
to clot.
Which also explains why one of the side effects of aspirin is a risk of bleeding.
Which can be serious, so again, don’t just grab aspirin off the shelf because we told
you it’s neat.
Ask your doctor.
Aspirin’s effects in preventing clotting signal production are relatively permanent.
Once aspirin has bound to COX-1, it doesn’t come back off.
The body has to make whole new platelets with fresh COX-1, and that takes a few days.
Taking even a small amount of aspirin daily keeps the new COX-1 molecules in those fresh
cells locked down too.
That’s why 81 mg per day is plenty for folks who are trying to avoid another heart attack
-- even a small amount of aspirin works great.
But because it’s absorbed by your body and goes to work pretty quickly, a full, pain-relief-strength
dose of 325 mg might be given as an intervention when someone is actually having a heart attack.
So now you know why a bottle of “baby” aspirin is actually for grown-ups -- and could
save their life.
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a dose of acetylsalicylic acid.
We’ll see you next week.