Now, excretion is our 4th and final
xcretion is just the removal of the
drugs from the body—
where in metabolism, the biggest
player was the liver—
excretion, the biggest player
are the kidneys.
They play a major role in
the rate of removal.
So if someone has kidney problems,
if they have kidney failure
or their kidneys are struggling,
this will increase your patient’s
risk of toxicity.
And remember, if someone
has kidney problems,
you want to make sure you
don’t want to give them
any drugs that could damage their kidneys.
So the processes of renal excretion
sound a little complicated,
but they’re really straightforward.
First of all, there is just
That means the drugs pass easily
through the capillary wall spaces
and into the urine in the proximal tubule.
There’s passive tubular reabsorption—
drugs move from the greater concentration
to a lower concentration or
active tubular secretions—
some of the drugs use active
to move from the blood into the urine.
These are just the 3 main processes
that the kidneys use
to take the drugs from the body and
help them leave or exit the body.
Now, there’s some other routes of excretion.
Not all drugs leave via the kidneys.
They’re not usually clinically
significant for most drugs
but there are some special cases,
so I wanted to make sure that
we mention these to you.
Some drugs leave through bile.
The bile secretes into the small intestines—
you’ve got a graphic there that
shows you the liver,
and the gallbladder is green
and where it connects,
and you’ve got your pancreas right there
and it all connects and meets
in the small intestine.
So in the bile, it's secreted into the small
intestines and it leaves in feces.
Some things may re-enter into the
a little bit through the hepatic vein, but
most of it will leave through the feces.
Other routes could be your lungs.
Now, that really applies
more to anesthetics if you’re
using gas anesthesia
then a route of excretion would be
you’re breathing back out that gas
which is why patients have
that really funky breath
after having some anesthesia.
Also, drugs can leave your body
through sweat and saliva
or even breast milk which is another reason
you want to be very careful
with which medications
you give to moms that are breastfeeding.
So, we talked about the main routes of
excretion are usually with the kidneys,
but there’s these other routes of excretion
that we wanted you to be aware of, but
you won’t see with most medications.
So, there you have it. There’s the 4
absorption, distribution, metabolism,
Your understanding of these
4 basic processes
will help you do safe and effective
with all of your patients.