Now, anticholinergic drugs - these guys
are a little more evolved, right?
They're a little more competitive.
They're also known as
Here's another word that we can break down.
Parasympatho- means parasympathetic, but
-lytic means boom! it's knockin it out.
Parasympathomimetic means it's just
like the parasympathetic system.
Parasympatholytic means boom!
It's against parasympathetic.
So parasympatholytic, anti - against, muscarinic
- that makes sense and muscarinic blockers.
It's pretty much all the same thing so anti-
is against, cholinergic - that makes sense
because these drugs slide on
into that cholinergic receptor.
Remember muscarinic receptors
are cholinergic receptors,
they slide on in and they block
anyone else from coming in.
That's why they're against, they're blockers so
I don't want to rush through that too quickly
So when you see these terms,
parasympatholytic drug -
that means that the reaction is going to be
against the parasympathetic nervous system
more like the sympathetic nervous system.
We can also call anti-muscarinic because anti
is against or blocking the muscarinic receptors.
or just plain old muscarinic blockers - they
all mean literally almost the same thing.
Okay, so anticholinergic produce the
selective blockade of muscarinic receptors,
it doesn't hit all the cholinergic receptors
but it hits some of the muscarinic receptors
Remember it competitively blocks the
action of acetylcholine it means,
"ha ha! i got there first, and
you can't have my seat", right?
It sits right in that muscarinic receptor.
But the key is most muscarinic receptors aren't structures
that are innervated by the parasympathetic nerves
that's why there's such a close relationship between if you
have an aganst that' s more of a parasympathetic response
or if you have an antagonist or a blocker -
it's more of a sympathetic response.
Okay, so we're back to our formula here, right?
How to study cholinergic drugs which we
know also works with adrenergic drugs but
today we're talking about cholinergic drugs.
You have to know the receptors that are involved,
you have to know what the name of the drug is
so we know what receptors are
involved and what the response is.
Well, we're talking about atropine
- that's our example drug.
You can see that the muscarinic receptors are
involved, they're located in the same places
that we were talking about earlier.
but because this is an antagonist,
it's gonna be a sympathomimetic
The other medication we talked about, bethanechol
was a - oh, I'm sorry my tongue is getting twisted!
Bethanechol is a parasympathomimetic,
but this drug is an antagonist,
it's a blocker so it acts more like
the sympathetic nervous system.
That's why it's sympathomimetic or
mimicking the sympathetic nervous system.
So you're gonna see opposite responses here,
more like the sympathetic nervous system.
Now look at what happens with this
particular drug, of atropine.
It will dilate the pupils.
Hey, that'll be kinda cool for doing,
looking at eye problems, right?
or for trying to look into someone's
eye, dilated pupils are really helpful.
It's gonna dry up their mouths so they're
gonna have less oral secretions, cool!
That'll be good in surgery because we don't want
you having a whole bunch of spit in your mouth
when we've got you under general anesthesia.
It's gonna increase your heartbeat.
whoo! I really like that one.
So you guys that are looking to go into critical care or ER,
this is really important that you know this medication.
We give it IV and it treats bradycardia
- a heart rate that's too slow.
Now, we would only give atropine for a slow
heart rate if the patient was symptomatic.
You can get some athletes and they're really like rock
stars and they come in with a heart rate in the low 50's
They're fine and their
blood pressure's fine.
But if we get somebody normally as hypertensive
and has a heart rate in a high 80s
and their heart rate dropped to below 50, we
might be giving them atropine right away.
This atropine is an antagonist.
It's gonna block the parasympathetic
The response? so we're gonna
see an increase in heartbeat.
So we use atropine for someone who's
bradycardic, and symptomatic with it.
The blood pressure is too low, they're feeling
dizzy, they'll show us all kinds of symptoms.
Now they'll open up the airways and will
also decrease the activity of the stomach
so somebody who's got really hypermotility of the stomach,
this medication might have some application there.
So that' why now when you look at the
list of therapeutic uses of atropine,
without looking back at
your notes, so you can say,
"Yeah, I understand why
it treats bradycardia."
Work through the rest of these - eye disorders,
preanesthetic or surviving muscarinic poisoning.