Let's move on to anticholinergics.
Cholinergic receptor antagonists
can be anti-nicotinic
and these are ganglion blockers,
neuromuscular junction blockers.
Let's talk about the ganglionic neurons
remember I was telling you that,
gangs go out in smoke so
ganglionic neurons are nicotinic.
Let's move on to the smooth
muscle and neuromuscular neurons.
Now, the smooth muscle neuromuscular
neurons are muscarinic.
The other types of end organs are
sweat glands which are also muscarinic.
How do I remember that?
Musky smell, means, sweat and muscles,
so that's how I tend to remember,
That smooth muscle and neuromuscular
neurons are muscarinic.
What are these antagonists?
Anti-muscarinic antagonists, the
non-selective one is atropine,
I already told you that it's used as
an antidote in sarin gas exposure.
It's also used in cardiac codes, the
M1 selective antimuscarinic drug.
Now drugs ending in “oxime,” like
pralidoxime are cholinesterase regenerators.
We spoke before about cholinesterase inhibitors,
this is where the double negative comes
in the central nervous system.
A cholinesterase inhibitor,
inhibits the enzyme that
breaks down acetylcholine.
So, a cholinesterase inhibitor
increases the amount of acetylcholine.
A cholinesterase regenerator
so, you reduce the amount of
acetylcholine in the synaptic cleft.
So, pralidoxime and other drugs in its class
will act on that synaptic
cleft to cause that effect.
Okay, we also use anti-muscarinic
agents in Parkinson’s disease.
triphenidyl, these are drugs,
that we're going to talk about later.
We use scopolamine in motion sickness.
It's available as a pill or patch,
most people know what a scopolamine patch is.
It's a very effective anti-nauseant.
And one other thing that I
think you need to remember
for when you're on the wards, is benztropine.
Benztropine is an antidote to acute dystonia,
where people are contracted and unable to move
and they often will have
their head turned to one side
as far as it'll go.
So benztropine is an antidote to that.
We're going to cover that
in a later lecture as well.
What are the effects on the eye?
Anti-muscarinic agents cause dilation, okay.
Atropine acts over 72 hours,
homatropine acts over 24 hours
and this one acts over 30 minutes.
Now atropine is derived from the belladonna plant,
which I have illustrated here.
It's a tertiary amine,
it's lipid soluble, it does
cross the blood-brain barrier
and its duration of action is around four hours.
In the lung, anticholinergics,
cause mild bronchodilation.
So, the prototypical drug
for the lung is ipratropium,
it's also known as atrovent.
So atrovent is the green inhaler.
The other bronchodilators like
tiotropium are also available
and are really making a huge
impact on respiratory therapy.
We're going to be talking about that in
our respiratory pharmacology lecture.
There is also a mild reduction
in airway secretions.
Atropine can sometimes be used as a direct agent,
when you're trying to intubate somebody
and they have tons of mucous secretions
and you can't see where you're going
with the intubation instrumentation.
We've also used it, I’ve also used it personally,
when I’m doing bronchoscopies,
because it does reduce airway secretion.
Okay, what about the effect on the
gut it's an anti-muscarinic agent.
Old treatments for peptic ulcer disease,
we no longer use them.
I just mentioned them here for your own interest,
it is not going to be on an exam
and it's not a big part of
our thought processes anymore.
In terms of the urinary tract,
reduce urgency and mild cystitis
and overactive bladder syndrome.
These are the various drugs
that we have available.
They're very commonly used in nursing homes.
It's worthwhile knowing these drugs
when you get out into practice.
Unfortunately, we use the trade name so much,
that the generic names kind
of fallen by the wayside
and it's because they sound so much like they
would relieve urinary symptoms
and they are listed here.
Okay, what about toxicity.
So, what happens if you take
too many anticholinergics.
We call this anticholinergic crisis
and this is a very old saying
and patients are dry as a bone,
hot as a pistol, red is a beat
and mad as a hatter.
So, patients who are dry, have
what we call, “Atropine fever.”
They're very dry, they're very warm,
they've lost the ability
to properly thermoregulate.
They're “Red as a beat,” because
they have peripheral vasodilation
and “Mad as a hatter,” they will have psychosis
and very bizarre kind of behavior.
Treat anticholinergic toxicity with physostigmine.
That is the antidote for that type of toxicity.
Well, there you have it, we
did a very difficult topic,
I think you guys are great to have
lasted until the end of this lecture.
This is the kind of stuff
that does show up on exams,
so, if you want to watch this
lecture again, I do encourage it.
I found it difficult when I was studying,
so, I tried to make it as easy as possible
and we do have some questions for you,
so, I encourage you to do
practice questions in this,
so, that when you get to your exam,
you'll nail it.
Thank you very much.