[♩INTRO ]
Ahh, winter.
The leaves have fallen, the breeze is chilly…
and cold season has arrived.
When that sticky cough and sniffly nose hits,
you probably cozy up with some hot soup, a
box of tissues, and your favorite brand of
cold medicine.
There are syrups, pills, and vaporizers to
treat about every symptom your cold can bring,
and they all involve some cool chemistry.
But before you down that bitter syrup, it
might also help to know that not every cold
medicine is as effective as you’d think.
Colds are some of the most common infectious
diseases we can get, but since they’re caused
by more than 200 different viruses, it’s
been basically impossible for us to create
a vaccine against them.
So the best we can do for now is fight the
symptoms.
Most cold symptoms are probably caused by
your body’s efforts to fight off the virus,
not the virus itself.
When you catch a cold, inflammatory proteins
like cytokines, get released and tell your
immune cells to get to work fixing the problem.
Mainly, they do this by dilating your blood
vessels so that infection-fighting white blood
cells can move around more easily.
Unfortunately, in your nose, those dilated
blood vessels also lead to tissue swelling
and congestion.
Cytokines also interact with pain receptors
in your esophagus, which can cause a sore
throat.
And in the nervous system, they can stimulate
various nerves to trigger a runny nose, sneezing
and coughing.
None of those things are especially fun -- okay,
really, they kind of stink.
So we’ve come up with all kinds of drugs
to knock them down as much as possible.
When your nose is stuffed up, you’ll probably
reach for a decongestant to clear up your
sinuses.
Pseudoephedrine is a popular one, found in
medications like Sudafed Decongestant and
Aleve D.
It’s a carbon ring attached to a complex
chain of other atoms, including nitrogen and
oxygen.
It reduces congestion by binding to receptors
in your nose, which makes the muscles around
your blood vessels tense up and reduces the
extra blood flow caused by cytokines.
Unfortunately, since pseudoephedrine is a
stimulant, it can also can cause insomnia,
nervousness, dizziness, and even affect your
heart rate.
It’s even been used Breaking Bad-style to
make methamphetamines illegally, which is
why it’s kept behind the pharmacy counter.
Phenylephrine is a similar medicine, found
in brands like Sudafed PE, but since it can’t
be used to make meth, it’s easier to buy.
Unfortunately, several studies have also found
that it doesn’t seem to be any more effective
than a placebo, which means it probably doesn’t
do much.
So, if that’s your favorite decongestant…
sorry.
Some colds can also cause chest congestion
and coughing.
To clear out some of that mucus, many medications
contain an expectorant, which helps you spit
up those lovely green gobs of phlegm.
***The most common one is called guaifenesin,
which is a carbon ring attached to chains
of oxygen, hydrogen, and carbon atoms.
It’s found in medicines like Mucinex.
We’re not entirely sure why it works, but
scientists think it suppresses the production
of mucins, one of the main proteins in the
mucus lining your lungs.
That makes it easier for specialized cells
to move mucus up and out of your body.
Still, that’s just based on research done
in a lab.
In patients, scientists have found that guaifenesin
does seems to help thin mucus, but it might
not be that effective at clearing it from
your lungs.
Some studies haven’t found much of an improvement
over a placebo in people with respiratory
infections.
But at least we know it helps somehow.
Now, maybe the most irritating symptom of
a cold -- for you and everyone around you
-- is that nasty, lasting cough.
To help calm it, many medications, including
Robitussin, contain a cough suppressant, like
dextromethorphan.
Dextromethorphan and molecules like it are
made up of four carbon rings, along with some
oxygen and nitrogen atoms.
They’re derived from morphine, a highly-addictive
painkiller, but at the doses used in cold
medicines, they don’t have the same potential
for abuse.
We’re not 100% sure how these molecules
work, but they probably work on the brain
instead of the respiratory system.
When you take dextromethorphan, it crosses
the blood-brain barrier -- the tightly-woven
net of cells in your brain’s blood vessels
that protect it from bacteria and infection.
And once it’s there, it affects a bunch
of different receptors.
Researchers think that it helps reduce coughing
by binding to receptors for neurotransmitters
called NMDA, sigma-1, and serotonin, since
other drugs that bind to them also seem to
suppress coughing.
Mainly, this tricks your brain into thinking
there’s no tickle in your throat and that
you don’t really need to cough.
Then again, some recent studies have also
found that dextromethorphan may not actually
be that effective, at least in kids, although
many studies don’t seem to be that reliable.
Outside of cold medicine, though, it does
have some uses.
Because of its effects on the nervous system,
it’s also being investigated for use in
a bunch of different conditions, like treating
anxiety and agitation in Alzheimer's disease
-- which is really cool.
Still, effective or not, all of these medications
only treat the symptoms of the cold.
None of them actually do anything to help
kill the virus or boost your immune system
-- except maybe by helping you sleep better.
Ultimately, the only thing that can cure a
cold is time!
But these medicines will hopefully make things
easier while you wait it out.
Thanks for watching this episode of SciShow!
Besides over-the-counter medicines, you’ve
probably heard how vitamin C or zinc can help
stop a cold -- but that’s not true.
And if you’d like to learn more, you can
watch our episode all about it to find out why.
[♩OUTRO ]
