Hi, welcome to this video
We're going to walk through
each of the 4 major processes
that are involved in moving
that drug through the body.
Let's get started.
What is pharmacokinetics?
Well, that's probably a word
you haven't thought of before.
So let's break it down for you.
Pharmacokinetics is the movement of the
drug through the body, from entry to exit.
And that means from the route that you
took it to when it leaves the body.
That involves absorption, distribution,
metabolism, and excretion.
So, as you're taking notes, as
we begin this presentation,
I want you to think about there's 4 main
processes that we're going to discuss:
how the drug is absorbed, how it's distributed,
how it's metabolized, and how it's excreted.
So let's take a look at absorption.
Now, the definition of absorption
is the movement of the drug
from the site of administration
to the bloodstream.
That's really simple, but there's lots
of routes that you can take a drug with.
So, we're talking about the movement of the drug
from the site that you give it to the bloodstream.
Now, this slide has an example of all the
different ways that you can give a drug.
Pretty much if you have an orifice, we
can give you a drug through it, right?
Oral, sublingual, in your eyes, in your ears,
and we can give it subcute, IM, IV,
and other more personal routes.
But we're talking about absorption,
which is from the point of entry
till we get to the bloodstream.
Now, 2 factors you want to keep in mind is the
rate of absorption and the amount of absorption.
The absorption rate is going to be higher
depending on the speed of the effect,
and the amount is going to determine
the intensity of the effect.
So, the absorption rate will determine
how quickly the patient feels
the effect of the medication.
The amount that's absorbed will be the
intensity of the effect the patient feels.
So let's look at things that
impact drug absorption.
First of all, it's how fast the drug can dissolve.
The quicker the drug dissolves, the faster
it's going to make it into the bloodstream.
The surface area also plays a role.
So, the larger the surface area, the faster
the drug will make it into the bloodstream.
The quality of blood flow is also really
important, the better the blood flow,
the faster the drug will make
it into the bloodstream.
The drug also has to have the
ability to cross a cell membrane.
So, the more easily a drug
crosses a cell membrane,
the faster it will make it into the bloodstream.
Now, pH partitioning and drug
ionization also plays a role.
Don't let that get you really excited.
It's not a big deal, but we're just talking
about the pH in the stomach is 1.3,
and it's 6 in the intestine.
And later on, we'll explain to you why that is so
important and how it impacts drug absorption.
So, the first pass effect is something that I
want you to keep in mind for oral medications.
Essentially, if you take a drug by
mouth, it goes into your stomach.
It's got to go through the liver before
it makes it into your bloodstream.
And a lot of the drug can
be inactivated by the liver,
and that's what we call the first pass effect.
Now although the first pass effect usually occurs in the
it can also occur in the lungs, the vasculature, the
, and other metabolically active tissues.
Now, that's the reason that
oral medication dosages
are much higher than IV medication dosages.
So keep that in mind.
First pass effect impacts oral drugs because
the drug goes in the mouth, into the stomach,
has to go through the liver, and a lot of the
drug becomes inactivated in a first pass effect.