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let's move on to the motility disorders
so the motility disorders can be treated
by several agents you have the dopamine
antagonists the motel and agonists the
laxatives and the anti diarrheal agents
let's start off with the : o mimetics so
: o mimetics lower the sphincter tone of
the lower esophageal sphincter now in
the past we use drugs like pathetic halt
but not anymore because pathetic all
tends to be a toxic agent and and
doesn't really work as well as we had
hoped
neostigmine which is an acetylcholine as
in hell in acetylcholine his inhibitor
is often used in the hospital for acute
bowel distension now for further
information on this particular agent I
encourage you to take a look at our
autonomic nervous system pharmacology
lectures you'll have a much better
discussion about this particular drug in
that lecture other agents include the
dopamine receptor antagonist
specifically the d2 receptors so
metoclopramide is your prototypical
example of this it causes d2 blockade
and this causes increased bowel transit
so things move a little bit quicker they
may also cause parkinsonian symptoms so
you have to be fairly careful with these
agents they work also in the area of a
streamer which is part of the emetic
center of the brain and that for that
reason it's a very effective antiemetic
in surgery and in cancer patients
domperidone is another example of these
type of agents it does not cross the
blood-brain barrier so it makes it a
little bit different from metoclopramide
and it's therefore less likely to cause
CNS effects not surprisingly the
antiemetic effects of domperidone are
really not that significant now motele
and receptor agonists are an interesting
group because the prototypical agent is
actually an antibiotic erythromycin it
directly stimulates Motel and receptors
and has benefits in patients with
gastroparesis now this also explains the
common cause common side effect of
diarrhea a
from Ison is hard on the system and most
patients who take erythromycin for an
infection complain of diarrhea and
that's because of direct motile and
receptor agonist activity let's take a
look at the laxatives now laxatives can
work in several different ways they can
be bulk forming so the classic example
of that is Salem now sigh ileum is a
seed and in order for it to work
properly it has to be chewed and not
just chewed but what we call masticated
and what we mean by that is that it has
to be chewed and mixed with saliva
because the salivary amylase will mix
with the Psy ileum and activate it now
there are over-the-counter agents that
are ground-up sigh ileum they come as a
as an orange kind of a powder that you
can spread on your eggs or mix with your
orange juice those are actually quite
effective over-the-counter agents such
as Metamucil contain Salem that hasn't
been activated now your herbalist
naturopath take people like to give
sytem seeds directly and that's fine
works really well as long as they chew
it and masticate it and mix it with
their saliva before they swallow it's
gross
so I don't know why you'd ever want to
choose to do that instead of just take
Metamucil
there are stool softening agents
docusate sodium is a very commonly used
agent I use it in probably 60% of my
patients over the age of 80 glycerine
tablets and blisterin suppositories and
mineral oil is also another way of
softening stool now osmotic Karthik's
work by actually causing more water to
be present in the stool so it's kind of
like creating a gel matrix within the
stool itself so that water stays in the
stool and that the stool is softer
magnesium oxide and all of these other
ones are examples of that now stimulants
act by actually irritating the bowel the
prototypical and very old example of
that is castor oil I'm sure you saw that
on Bugs Bunny when you know they gave
the coyote some stimulant and he had to
go to the bathroom really quickly at
least that's how I remember Castro it's
not used anymore
we now use things like aloe and Senna
which are probably more gentle and
and easier on the system chloride
channel activators are less used at this
point in time how they work is by
increasing fluid bulk within the stool
itself and finally the opioid receptor
antagonists are an interesting way of
treating treating patients what happens
is is that we know that opioids are
constipating by blocking the opioid
receptor we believe that this will
reduce constipation particularly in
those patients who are on opioids so
there you have the list of the laxatives
have a look at this we're going to
present this slide to you as a
downloadable slide so that you can have
this in your own slide library let's
take a look at some of these other
agents now we to you before about
opioids being constipating we can
actually use opioids as anti diarrheal
agents as well and that seems logical
because opioids are constipating in and
of themselves however we don't want to
use strong lock the opioids and we
actually have an agent that is a weak
opioid it's commonly sold as imodium
it's a analog of meperidine it has a
minimal central nervous system effects
and maximum GI effects originally when
this agent was released on the market we
thought we would be using it for pain
control and the GI effects were so bad
that people complained about it but some
enterprising scientist at the drug
company said well why don't we use it
for diarrhea and actually it works
really well
so imodium is probably the number one
selling over-the-counter agent for the
use in anti diarrheal treatment other
anti diarrheal agents include Kaylin
so Kaylin is a naturally found magnesium
aluminum silicon and it's hydrated so it
works quite well pectin is an
indigestible carbohydrate that comes
from Apple's now the interesting thing
about pectin is that it actually absorbs
bacterial toxins and some fluids so when
you combine Kailyn and pectin you come
up with an
agent called kaopectate which is sold
commercially now this agent can of
course cause constipation but when
you're giving a patient with diarrhea
this agent it works quite nicely now the
problem with kaopectate is because it's
one of these binders that binds toxin if
you think about it it'll also interfere
with the absorption of a whole host of
medications so patients on kaopectate be
aware that your other medications are
probably being bound it's really
important I'm just going to stop here
and I'm going to say do not use anti
diarrheal agents in patients of a bloody
diarrhea or infectious diarrhea because
the diarrhea in those cases are actually
cathartic in the truest sense of the
word meaning that you're getting rid of
the infectious agent and diarrhea in
this case is a protective mechanism from
the disease so if you inhibit the
protective mechanism you make the person
much sicker we're going to cover this in
more detail in your GI systems lecture
by lecture you later but I just want to
put that out there now
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you